setup playbook and heartbeat for isolated deployments

* Allow isolated_group_ use in setup playbook
* Tweaks to host/queue registration commands complementing setup
* Create isolated heartbeat task and check capacity
* Add content about isolated instances to acceptance docs

awx/playbooks/heartbeat_isolated.yml

@@ -0,0 +1,16 @@
+---
+
+# The following variables will be set by the runner of this playbook:
+# job_id_cutoff: <pk>
+
+- hosts: all
+  gather_facts: false
+
+  tasks:
+
+    - name: Get capacity of the instance
+      tower_capacity:
+      register: result
+
+    - name: Print capacity in escaped string to scrape out
+      debug: msg="{{ start_delimiter|default('') }}{{ result['capacity'] }}{{ end_delimiter|default('') }}"