Allow to pass --insecure options into VMs

currently Heat tests have troubles running when self-signed SSL CA is
used on public Heat API and standard upstream images (Cirros, Ubuntu)
are used as those lack trust to those CA - example is DevStack
with tls-proxy service enabled.

A workaround is to set [clients_heat]insecure=True, but that is
not really a production-ready setting, and does not work for CFN-style
signaling, only for WaitConditions.

Instead, this patch adds an extra config option
`vm_to_heat_api_insecure` (defaults to False), and when enabled tests will
pass the correct option to the curl or cfn-signal commands running from
instance's user data via new parameters that test templates are now
accepting.

Change-Id: I94a82caf1fcb6999151ff1e6fbbe1e2ba211bbb9
diff --git a/heat_tempest_plugin/config.py b/heat_tempest_plugin/config.py
index c30981c..d572340 100644
--- a/heat_tempest_plugin/config.py
+++ b/heat_tempest_plugin/config.py
@@ -162,6 +162,11 @@
     cfg.StrOpt('credential_secret_id',
                help="Barbican secret id which storing cloud credential in "
                "remote site."),
+    cfg.BoolOpt('vm_to_heat_api_insecure',
+                default=False,
+                help="Set this to True if VM images used for tests "
+                     "can not verify a (self-signed) SSL certificate "
+                     "of public Heat endpoint."),
 ]
 
 heat_features_group = cfg.OptGroup(