Move heat_available option to service_available

This commit moves the heat_available config option from the
orchestration group to under the service_available group. The option
is also renamed to heat.

Change-Id: I86c93331a53b5a7323afe27839338ffa1428015f
diff --git a/tempest/config.py b/tempest/config.py
index 5eb52dc..d9de205 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -391,9 +391,6 @@
     cfg.IntOpt('build_timeout',
                default=300,
                help="Timeout in seconds to wait for a stack to build."),
-    cfg.BoolOpt('heat_available',
-                default=False,
-                help="Whether or not Heat is expected to be available"),
     cfg.StrOpt('instance_type',
                default='m1.micro',
                help="Instance type for tests. Needs to be big enough for a "
@@ -554,6 +551,9 @@
     cfg.BoolOpt('nova',
                 default=True,
                 help="Whether or not nova is expected to be available"),
+    cfg.BoolOpt('heat',
+                default=False,
+                help="Whether or not Heat is expected to be available"),
 ]