1146294 - do not import pulp.bindings.server to get DEFAULT_CA_PATH

The katello agent should not require the pulp bindings to be installed to
access this constant.
Merge pull request #593 from beav/move-constant

1146294 - do not import pulp.bindings.server to get DEFAULT_CA_PATH
Merge remote-tracking branch 'origin/2.5-dev'