Big Switch: Check source_address attribute exists

Check that the source_address attribute exists on
HTTPSConnection objects before referencing it since
it's not present on python 2.6 deployments. If it
does not exist, create a socket connection without
specifying the source.

Closes-Bug: #1316382
Change-Id: Ica10d23cc6de81ae56f711937f208c7321c77f36
Merge "Big Switch: Check source_address attribute exists"