Heat integration tests failing against https endpoints

Provide ca_file option to pass the ca certificate to verify https
connection. Also pass verify parameter to the test cases which
directly call requests library methods.

Change-Id: I4a81047136d6a64b151180e95c254edea8165349
Closes-Bug: #1553898
diff --git a/common/config.py b/common/config.py
index 6d35600..f8ae075 100644
--- a/common/config.py
+++ b/common/config.py
@@ -60,6 +60,10 @@
     cfg.BoolOpt('disable_ssl_certificate_validation',
                 default=False,
                 help="Set to True if using self-signed SSL certificates."),
+    cfg.StrOpt('ca_file',
+               default=None,
+               help="CA certificate to pass for servers that have "
+                    "https endpoint."),
     cfg.IntOpt('build_interval',
                default=4,
                help="Time in seconds between build status checks."),