support running singular test-cases

provide the -o/--only option to specify the 'only' test case to run within a particular suite.
supports specifying TestClass as prefix or using --suite option, for instance:

upr suite is assumed by default:
./pyupr -b dev -h 192.168.1.120:9000 -o test_open_consumer_connection_command

specify suite:
./pyupr -b dev -h 192.168.1.120:9000 -o test_stat_vbucket_seqno  -s mcd

class prefix:
./pyupr -b dev -h 192.168.1.120:9000 -o McdTestCase.test_stat_vbucket_seqno

Change-Id: I29a733ae68e953f2958ed61bb00e760c5f20bf38
Merge "support running singular test-cases"