qa/standalone: create mon-stretch standalone test

Separate `mon-stretch` from `mon`.

Renamed `mon-stretched-cluster.sh` to
`mon-stretch-fail-recovery.sh`.

This isolation of stretch cluster test will enable
developers to get results faster for stretch-cluster
related stuff.

Signed-off-by: Kamoltat <ksirivad@redhat.com>

qa/standalone/mon-stretch/mon-stretch-fail-recovery.sh

@@ -146,4 +146,4 @@ EOF
     teardown $dir || return 1
 
 }
-main mon-stretched-cluster "$@"
+main mon-stretch-fail-recovery "$@"

qa/suites/rados/standalone/workloads/mon-stretch.yaml

@@ -0,0 +1,18 @@
+roles:
+- - mon.a
+  - mgr.x
+  - osd.0
+  - osd.1
+  - osd.2
+  - client.0
+openstack:
+  - volumes: # attached to each instance
+      count: 3
+      size: 10 # GB
+tasks:
+- install:
+- workunit:
+    basedir: qa/standalone
+    clients:
+      all:
+        - mon-stretch