Cleanup: Rename 'bus_message' callback function to 'on_match'
Cleanup: Rename 'bus_message' callback function to 'on_match'

It is clearer for this function's name to reflect what it does, rather
than when it is called. Particularly important now that we have several
message handlers.

LewisHaley/stb-tester,stb-tester/stb-tester,wmanley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,wmanley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,wmanley/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,wmanley/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester