test/rilmodem/sim: updates to testsimutil

Add arg parsing support for enable/disable
PIN locking tests.  Also, in validate_sim_props,
only check 'PinRequired', not 'LockedPins'.
test/rilmodem/sim: update test-sim* scripts

Update test-sim-* scripts based on changes to
simtestutil module for disable/enable PIN
lock tests.
test/rilmodem/sim: disable/enable SIM lock tests

Add tests for enabling/disabling SIM PIN locking.
test/rilmodem/sim: fix test-sim-enable-pin-lock
test/rilmodem/sim: add change-pin test
Merge pull request #137 from tonyespy/sim-locking-tests

Sim locking tests