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/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 3579026..a73e8a0 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -306,9 +306,6 @@
 # tests spawn full VMs, which could be slow if the test is already in a VM.
 build_timeout = 300
 
-# Whether or not Heat is expected to be available
-heat_available = false
-
 # Instance type for tests. Needs to be big enough for a
 # full OS plus the test workload
 instance_type = m1.micro
@@ -358,3 +355,5 @@
 swift = True
 # Whether or not nova is expected to be available
 nova = True
+# Whether or not Heat is expected to be available
+heat = false