VkConfig: Fix tray combo-box signal method

[npavlicek]

The combo-box for selecting what layers are being controlled is not correctly signaling its corresponding slot. As a result the configurator never gets updated. Checkable actions use the "toggled" signal rather than "triggered". A simple if statement was also added so only the selected action updates the configurator.

2046

[CLAassistant]

All committers have signed the CLA.

[ci-tester-lunarg]

Author npavlicek not on autobuild list. Waiting for curator authorization before starting CI build.

[christophe-lunarg]

Thanks for contributing!