About Plugins: Fix that disabling plugin could disable too many others

Only disable plugin rows with disabled *Required* plugin dependencies.

Change 044eeacd introduces another
dependency type "Test", which are actually not dependencies in a strict
sense and even can be cyclic, which makes this bug especially obvious.

Change-Id: Ie504b4dd52670d838b712e88ae2e42123975b1d5
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: hjk <hjk@theqtcompany.com>