Add more TLS protocols to rabbit impl

Python 2.7.9 added PROTOCOL_TLSv1_1 and PROTOCOL_TLSv1_2, so these
are added to the allowed kombu_ssl_version values.

See https://docs.python.org/2/library/ssl.html#ssl.PROTOCOL_TLSv1_1

Change-Id: I1dd590d916ab524284a941db91b9cb81fd4639bb
Merge "Add more TLS protocols to rabbit impl"