Switch all client crypto operations over to OpenSSL

Acceptance criteria:

• Client contains no Golang imports starting with crypto.
• All current TLS mechanisms are replaced with golang-openssl.
  • The original is https://github.com/spacemonkey/golang-openssl, but currently https://github.com/Linutronix/golang-openssl is being used due to some extra requirements
• All existing unit, acceptance and integration tests must pass.