Correct Player.PlayPause behavior

In current implementation using play parameter as boolean won't force the playerspeed to 1 as it should.
This PR correct this so that using a bool parameter act as the toggle and provide the same behavior as GUI or EventServer.
Merge pull request #2301 from Tolriq/CorrectPlayPause

jsonrpc: correct Player.PlayPause behavior
Merge remote-tracking branch 'upstream/master'