[driver tests] Improve vmdk_ops test

[shuklanirdesh82]

need to supply unique vm/tenant name for vmdk_ops_test

Following tests are failing because of reusing the same name for vm/tenant name

OTOMH few tasks:

• getting rid off static value for vm name (e.g. vm_name = 'test-vm', tests_vmX)
• need to improve tearDown() method to cleanup the created VMs
• Need to improve following validation

        result = vmdk_ops.executeRequest(vm1_uuid, self.vm1_name, self.vm1_config_path, 'list', None, opts)
       
        self.assertEqual(3, len(result))
        self.assertEqual("tenant1_vol1", result[0]['Name'])
        self.assertEqual("tenant1_vol2", result[1]['Name'])
        self.assertEqual("tenant1_vol3", result[2]['Name'])

• need to use vmdk_utils.get_datastores() instead of hardcoded value ('datastore1')
• need to fix following code block as it is complaining when there is only one datastore in the inventory

               if len(datastores) >= 1:
 730                     datastore1 = datastores[1]
 731                     self.datastore1_name = datastore1[0]
 732                     self.datastoer1_path = datastore[2]

3 tests are failing locally consistently whereas 'testAttachDetach' passes if the created test-vm is not present in the inventory.

Running unit tests in /tmp/vmdk_ops_unittest3019/vmdk_ops_test.py...
..E.E........FF.
======================================================================
ERROR: testAttachDetach (__main__.VmdkAttachDetachTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/vmdk_ops_unittest3019/vmdk_ops_test.py", line 531, in testAttachDetach
    vm=vm[0])
IndexError: list index out of range

======================================================================
ERROR: testBadOpts (__main__.VmdkCreateCloneRemoveTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/vmdk_ops_unittest3019/vmdk_ops_test.py", line 272, in setUp
    path, err = vmdk_ops.get_vol_path(self.vm_datastore, auth.DEFAULT_TENANT)
  File "/tmp/vmdk_ops_unittest3019/vmdk_ops.py", line 638, in get_vol_path
    os.symlink(path, symlink_path)
OSError: [Errno 17] File exists

======================================================================
FAIL: test_vmdkops_on_different_tenants (__main__.VmdkTenantTestCase)
Test vmdkops on VMs which belong to different tenant
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/vmdk_ops_unittest3019/vmdk_ops_test.py", line 1073, in test_vmdkops_on_different_tenants
    self.assertEqual("tenant1_vol1", result[0]['Name'])
AssertionError: 'tenant1_vol1' != 'tenant1_vol3'

======================================================================
FAIL: test_vmdkops_on_tenant_vm (__main__.VmdkTenantTestCase)
Test vmdk life cycle on a VM which belongs to a tenant
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/vmdk_ops_unittest3019/vmdk_ops_test.py", line 958, in test_vmdkops_on_tenant_vm
    self.assertEqual("tenant1_vol2", result[0]['Name'])
AssertionError: 'tenant1_vol2' != 'tenant1_vol3'

----------------------------------------------------------------------
Ran 16 tests in 85.312s

FAILED (failures=2, errors=2)

//CC @kerneltime @ashahi1

[shuklanirdesh82]

//CC @shaominchen @lipingxue (CC'ing them as they have run into the issue)

Please feel free to add more improvement if you have come across and not listed first comment.

Thanks!