Fix testcase 'TestPortsV2.test_range_allocation' failed randomly

Fix bug 1179370

Change-Id: Id5645546c98549c9d7cf68359e0f6fa128ad84b7
Signed-off-by: Christoph Thiel <c.thiel@telekom.de>
Merge "Fix testcase 'TestPortsV2.test_range_allocation' failed randomly" into stable/grizzly