BUG/MEDIUM: ssl: first outgoing connection would fail with {ca,crt}-ignore-err

BUG/MEDIUM: ssl: first outgoing connection would fail with {ca,crt}-ignore-err

When using ca_ignore_err/crt_ignore_err, a connection to an untrusted
server raises an error which is ignored. But the next SSL_read() that
encounters EAGAIN raises the error again, breaking the connection.

Subsequent connections don't have this problem because the session has
been stored and is correctly reused without performing a verify again.

The solution consists in correctly flushing the SSL error stack when
ignoring the crt/ca error.