Using the cinderclient to fetch server versions will fail with error
`OpenSSL.SSL.Error: [sslv3 alert handshake failure]` when the server
requires client certificates to be passed with these requests.
Added the optional parameter `cert` to both get_server_version
get_highest_client_server_version and methods so that users can have
the option to pass client certificates while fetching server versions.
Also support passing mTLS certificate/key to HTTPClient
Closes-Bug: #1915996
Change-Id: I57c665dd9d4b8c32e5f10994d891d1e0f5315548
Signed-off-by: sri harsha mekala <smekala@oath.com>
9c2e8df948