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/test.py b/common/test.py
index 4eaa2b7..42fa43c 100644
--- a/common/test.py
+++ b/common/test.py
@@ -92,6 +92,10 @@
         self.metering_client = self.manager.metering_client
         self.useFixture(fixtures.FakeLogger(format=_LOG_FORMAT))
         self.updated_time = {}
+        if self.conf.disable_ssl_certificate_validation:
+            self.verify_cert = False
+        else:
+            self.verify_cert = self.conf.ca_file or True
 
     def get_remote_client(self, server_or_ip, username, private_key=None):
         if isinstance(server_or_ip, six.string_types):