CLOUDSTACK-4648: Fixed Snapshots test cases

Fixed following test cases:
1) test_01_volume_from_snapshot
2) test_03_snapshot_detachedDisk
3) test_07_template_from_snapshot

All three test cases are running successfully on XenServer but test cases (01 and 07) failing on KVM due to a common issue.
Product defect logged for this: https://issues.apache.org/jira/browse/CLOUDSTACK-5097

test_03 is running ok on KVM too, the problem was - disk was not getting detached because it was not unmounted before detaching. Added code to unmount the disk.

Signed-off-by: Girish Shilamkar <girish@clogeny.com>
CLOUDSTACK-4885: basic timing profiler for tests

This will add time taken in seconds along with start and end timestamp
logging facility for test cases.Currently this is not
available for console logs

Signed-off-by: Santhosh Edukulla <Santhosh.Edukulla@citrix.com>
Adding readable start and end time stamps

Signed-off-by: Santhosh Edukulla <Santhosh.Edukulla@citrix.com>