Description of problem:
Sometimes cluster import fails with error `Import existing Gluster Cluster` when imported with specified Cluster Name. It happens on a fresh setup where import didn't happen yet.

Example of errors:
```
Aug  8 01:01:17 fbalak-usm1-gl2 journal: 2018-08-07 23:01:17.671554+00:00 - node_agent - /usr/lib/python2.7/site-packages/tendrl/commons/jobs/__init__.py:288 - process_job - ERROR - Failure in Job d12e069b-aa20-429c-b34a-86d8276669d7 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 240, in process_job#012    the_flow.run()#012  File "/usr/lib/python2.7/site-packages/tendrl/commons/flows/import_cluster/__init__.py", line 131, in run#012    exc_traceback)#012FlowExecutionFailedError: ['Traceback (most recent call last):\n', '  File "/usr/lib/python2.7/site-packages/tendrl/commons/flows/import_cluster/__init__.py", line 98, in run\n    super(ImportCluster, self).run()\n', '  File "/usr/lib/python2.7/site-packages/tendrl/commons/flows/__init__.py", line 186, in run\n    (atom_fqn, self._defs[\'help\'])\n', 'AtomExecutionFailedError: Atom Execution failed. Error: Error executing atom: tendrl.objects.Cluster.atoms.ImportCluster on flow: Import existing Gluster Cluster\n']#012 - FlowExecutionFailedError: [{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': 240, 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': 131, u'file': u'/usr/lib/python2.7/site-packages/tendrl/commons/flows/import_cluster/__init__.py', u'statement': u'exc_traceback)'}]

Aug  8 01:01:17 fbalak-usm1-gl2 journal: 2018-08-07 23:01:17.690306+00:00 - node_agent - /usr/lib/python2.7/site-packages/tendrl/commons/jobs/__init__.py:298 - process_job - ERROR - d12e069b-aa20-429c-b34a-86d8276669d7:Failure in Job d12e069b-aa20-429c-b34a-86d8276669d7 Flow tendrl.flows.ImportCluster with error:#012Traceback (most recent call last):#012  File "/usr/lib/python2.7/site-packages/tendrl/commons/jobs/__init__.py", line 240, in process_job#012    the_flow.run()#012  File "/usr/lib/python2.7/site-packages/tendrl/commons/flows/import_cluster/__init__.py", line 131, in run#012    exc_traceback)#012FlowExecutionFailedError: ['Traceback (most recent call last):\n', '  File "/usr/lib/python2.7/site-packages/tendrl/commons/flows/import_cluster/__init__.py", line 98, in run\n    super(ImportCluster, self).run()\n', '  File "/usr/lib/python2.7/site-packages/tendrl/commons/flows/__init__.py", line 186, in run\n    (atom_fqn, self._defs[\'help\'])\n', 'AtomExecutionFailedError: Atom Execution failed. Error: Error executing atom: tendrl.objects.Cluster.atoms.ImportCluster on flow: Import existing Gluster Cluster\n']
```

Version-Release number of selected component (if applicable):
tendrl-ansible-1.6.3-6.el7rhgs.noarch
tendrl-api-1.6.3-5.el7rhgs.noarch
tendrl-api-httpd-1.6.3-5.el7rhgs.noarch
tendrl-commons-1.6.3-11.el7rhgs.noarch
tendrl-grafana-plugins-1.6.3-8.el7rhgs.noarch
tendrl-grafana-selinux-1.5.4-2.el7rhgs.noarch
tendrl-monitoring-integration-1.6.3-8.el7rhgs.noarch
tendrl-node-agent-1.6.3-9.el7rhgs.noarch
tendrl-notifier-1.6.3-4.el7rhgs.noarch
tendrl-selinux-1.5.4-2.el7rhgs.noarch
tendrl-ui-1.6.3-9.el7rhgs.noarch

How reproducible:
7% (I ran 100 import experiments automatically, in 7 cases this error appeared)

Steps to Reproduce:
1. Import cluster with 2 volumes, set Cluster Name parameter.
2. Open task detail.

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

Expected results:
Import should succeed.

Additional info: