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/lib/management_modules/tower_capacity.py

@@ -0,0 +1,40 @@
+# Copyright (c) 2017 Ansible by Red Hat
+#
+# This file is part of Ansible Tower, but depends on code imported from Ansible.
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+from ansible.module_utils.basic import AnsibleModule
+
+import subprocess
+
+
+def main():
+    module = AnsibleModule(
+        argument_spec = dict()
+    )
+    # Duplicated with awx.main.utils.common.get_system_task_capacity
+    proc = subprocess.Popen(['free', '-m'], stdout=subprocess.PIPE)
+    out,err = proc.communicate()
+    total_mem_value = out.split()[7]
+    if int(total_mem_value) <= 2048:
+        cap = 50
+    cap = 50 + ((int(total_mem_value) / 1024) - 2) * 75
+
+    # Module never results in a change and (hopefully) never fails
+    module.exit_json(changed=False, capacity=cap)
+
+
+if __name__ == '__main__':
+    main()