Adb screenrecord test: feature requests implementation + bugfix

Refactoring code - utilizing TestRunHelper class.
Also swapping unlock() for disableKeyguard()

63060822: Need to convert field string values to numbers, otherwise
it will not work with blackbox

Bug: 63114860
Bug: 63060822
Fixes: 63114860
Test: tradefed.sh run google/test/framework/media/adb-screen-record
 -s <device serial number>

Change-Id: I3c9919145868914314d0af906696445f03926691