Bug 1599375

Description of problem:
This BZ is based on findings from BZ 1571809.
I have done 90 experiments where I did cluster import with specified Cluster Name, saved the results, reverted snapshots of hosts and triggered import again. 8 experiments failed with `Import existing Gluster Cluster` message like:
```
ERROR - Failure in Job b451fa27-1b1f-4485-9b31-edda7c85f829 Flow tendrl.flows.ImportCluster with error:Traceback (most recent call last):#012  File "/usr/lib/python2.7/site-packages/tendrl/commons/jobs/__init__.py", line 242, in process_job#012    the_flow.run()#012  File "/usr/lib/python2.7/site-packages/tendrl/commons/flows/import_cluster/__init__.py", line 124, in run#012    raise ex#012AtomExecutionFailedError: Atom Execution failed. Error: Error executing pre run function: tendrl.objects.Cluster.atoms.CheckClusterNodesUp for flow: Import existing Gluster Cluster#012 - AtomExecutionFailedError: [{u'function': u'__bootstrap', u'line': 785, u'file': u'/usr/lib64/python2.7/threading.py', u'statement': u'self.__bootstrap_inner()'}, {u'function': u'__bootstrap_inner', u'line': 812, u'file': u'/usr/lib64/python2.7/threading.py', u'statement': u'self.run()'}, {u'function': u'run', u'line': 765, u'file': u'/usr/lib64/python2.7/threading.py', u'statement': u'self.__target(*self.__args, **self.__kwargs)'}, {u'function': u'process_job', u'line': 242, u'file': u'/usr/lib/python2.7/site-packages/tendrl/commons/jobs/__init__.py', u'statement': u'the_flow.run()'}, {u'function': u'run', u'line': 124, u'file': u'/usr/lib/python2.7/site-packages/tendrl/commons/flows/import_cluster/__init__.py', u'statement': u'raise ex'}]

```

Version-Release number of selected component (if applicable):
tendrl-ansible-1.6.3-5.el7rhgs.noarch
tendrl-api-1.6.3-3.el7rhgs.noarch
tendrl-api-httpd-1.6.3-3.el7rhgs.noarch
tendrl-commons-1.6.3-7.el7rhgs.noarch
tendrl-grafana-plugins-1.6.3-5.el7rhgs.noarch
tendrl-grafana-selinux-1.5.4-2.el7rhgs.noarch
tendrl-monitoring-integration-1.6.3-5.el7rhgs.noarch
tendrl-node-agent-1.6.3-7.el7rhgs.noarch
tendrl-notifier-1.6.3-4.el7rhgs.noarch
tendrl-selinux-1.5.4-2.el7rhgs.noarch
tendrl-ui-1.6.3-4.el7rhgs.noarch

How reproducible:
9%

Steps to Reproduce:
1. Install tendrl.
2. Import cluster, don't set Cluster Name parameter.
3. Open task detail.

Actual results:
In some cases there happens to appear an error and import fails.

Expected results:
Import should succeed.

Additional info:
Logs and config files from these experiments are on this address:
http://file.brq.redhat.com/~fbalak/bz/1571809/results.tar.gz