Fix vibrator compose VTS tests

Add TearDown method to reset the vibrator state between tests to avoid
illegal state errors caused by unrelated tests.

Add calls to vibrator->off between vibrator->compose invocations within
the same test, so calls are tested individually.

Test runs with this change on failing targets:

Bug: 323087313
Test: atest VtsHalVibratorTargetTest
Change-Id: I1e9aa243da07040b33df2474977fc8becac440a5