Makes ca_file parameter optional when use_ssl => true

The ca_file parameter should not be required when use_ssl => true.  Rather,
use_ssl must be true when ca_file is specified.

Change-Id: Ifb4b5acccdce0be63e763b4d837eb452827cd6d4
Closes-Bug: 1356089
(cherry picked from commit 70ef4af1e7c5b42a4ebabdbd6d2f69623c8861f5)
Merge "Makes ca_file parameter optional when use_ssl => true" into stable/icehouse