Remove duplicate connection logic when verifying default credentials

The ```.raw_connect``` method was updated to pass ```:verify_ssl => false``` and connections were working, but when testing the credential verification button in the UI I found that connections would fail due to an SSLv3 error.  Sharing the same connection logic is a much safer (especially when we are trying to verify that we can establish a connection to the system).
@brandondunne 
Previously, we raised if rhevm.api is nil.  Now, we raise only if `connect(options).api` raises an exception.

Is this the desired behavior?