LU-1999 test: LW conn test should rely on debug logs

LU-1999 test: LW conn test should rely on debug logs

Recovery-small test 6 should rely on lustre debug logs instead of
dmesg since console messages are rate limited and might not be printed
as expected by the test.

The test should also be skipped if the server does not support
lightweight connections (i.e. is older than 2.3.50).

Signed-off-by: Johann Lombardi <johann.lombardi@intel.com>
Change-Id: I78994831506e632f1730eb6f80fe145c7fc2cf3e
Reviewed-on: http://review.whamcloud.com/4288
Tested-by: Hudson
Reviewed-by: Li Wei <liwei@whamcloud.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>