files converted to directories are not changed back on later recursive copy

As a result of bugs like #6027, some files which are supposed to be copied down by CFEngine are created as (or converted to) directories. Unfortunately, they are never changed back - once a file is a directory, CFEngine happily leaves it that way while reporting that all is well. I have this happen with remote copies, but it apparently affects local copies as well.

Here are the steps to reproduce, demonstrating a successful copy if the files aren't there, and a failure to replace an existing directory with a file.

<pre>
user@host [/home/user]
$ mkdir -p /tmp/src
user@host [/home/user]
$ touch /tmp/src/file

{1,2}
user@host [/home/user]
$ mkdir -p /tmp/src/dir{1,2}

user@host [/home/user]
$ cat ./test.cf
bundle agent test {
files:
"/tmp/dst/"
copy_from => tst,
move_obstructions => "true",
depth_search => recurse("inf");
}

body depth_search recurse(d) {
depth => "$(d)";
xdev => "true";
}

body copy_from tst {
source => "/tmp/src";
compare => "digest";
}
user@host [/home/user]
$ sudo cf-agent -lIKf ./test.cf -b test
2015-11-30T17:45:37-0600 info: Using command line specified bundlesequence
2015-11-30T17:45:37-0600 info: Copying from 'localhost:/tmp/src/file2'
2015-11-30T17:45:37-0600 info: Copying from 'localhost:/tmp/src/file1'
user@host [/home/user]
$ ls -la /tmp/dst
total 16
drwxr-xr-x 4 root root 4096 Nov 30 17:45 .
drwxrwxrwt. 18 root root 4096 Nov 30 17:45 ..
drwx------ 2 root root 4096 Nov 30 17:45 dir1
drwx------ 2 root root 4096 Nov 30 17:45 dir2
rw-r---- 1 root root 0 Nov 30 17:45 file1
rw-r---- 1 root root 0 Nov 30 17:45 file2
user@host [/home/user]
$ sudo cf-agent -ldKf ./test.cf -b test | grep file1
2015-11-30T17:46:06-0600 verbose: Destination file '/tmp/dst/file1' already exists
2015-11-30T17:46:06-0600 verbose: File permissions on '/tmp/dst/file1' as promised
2015-11-30T17:46:06-0600 verbose: File '/tmp/dst/file1' is an up to date copy of source
user@host [/home/user]
$ sudo rm /tmp/dst/file1 && sudo mkdir -p /tmp/dst/file1
user@host [/home/user]
$ ls -la /tmp/dst
total 20
drwxr-xr-x 5 root root 4096 Nov 30 17:46 .
drwxrwxrwt. 18 root root 4096 Nov 30 17:46 ..
drwx------ 2 root root 4096 Nov 30 17:45 dir1
drwx------ 2 root root 4096 Nov 30 17:45 dir2
drwxr-x--- 2 root root 4096 Nov 30 17:46 file1
rw-r---- 1 root root 0 Nov 30 17:45 file2
user@host [/home/user]
$ sudo cf-agent -ldKf ./test.cf -b test | grep file1
2015-11-30T17:46:25-0600 verbose: Destination file '/tmp/dst/file1' already exists
2015-11-30T17:46:25-0600 verbose: File permissions on '/tmp/dst/file1' as promised
2015-11-30T17:46:25-0600 verbose: File '/tmp/dst/file1' is an up to date copy of source
user@host [/home/user]
$ ls -la /tmp/dst
total 20
drwxr-xr-x 5 root root 4096 Nov 30 17:46 .
drwxrwxrwt. 18 root root 4096 Nov 30 17:46 ..
drwx------ 2 root root 4096 Nov 30 17:45 dir1
drwx------ 2 root root 4096 Nov 30 17:45 dir2
drwxr-x--- 2 root root 4096 Nov 30 17:46 file1
rw-r---- 1 root root 0 Nov 30 17:45 file2
user@host [/home/user]
$ ls -la /tmp/src/
total 16
drwxr-x--- 4 q0px usec_pm 4096 Nov 30 17:36 .
drwxrwxrwt. 18 bin bin 4096 Nov 30 17:56 ..
drwxr-x--- 2 q0px usec_pm 4096 Nov 30 17:36 dir1
drwxr-x--- 2 q0px usec_pm 4096 Nov 30 17:36 dir2
rw-r---- 1 q0px usec_pm 0 Nov 30 17:36 file1
rw-r---- 1 q0px usec_pm 0 Nov 30 17:36 file2
</pre>

Here also are the extra debug lines around the file1 comparison:

<pre>
verbose: File '/tmp/dst/file2' is an up to date copy of source
verbose: Destination file '/tmp/dst/file1' already exists
verbose: Checksum comparison replaced by ctime: files not regular
debug: Directory...fixing x bits
debug: File okay, newperm '750', stat '750'
verbose: Additional promise info: source path './test.cf' at line 3
verbose: File permissions on '/tmp/dst/file1' as promised
verbose: Additional promise info: source path './test.cf' at line 3
verbose: File '/tmp/dst/file1' is an up to date copy of source
debug: Filename '/tmp/src/..' is classified as ignorable
verbose: Entering '/tmp/dst/dir2'
</pre>