improve and clean up audiod_status_dump()

Currently, no status is printed if audiod is off. This is suboptimal
as the _audiod_ status items should be sent in any case. This patch also

	- gets rid of some static variables in audiod_status_dump()
	- improves readability of audiod_status_dump()
	- moves dump_empty_status() from stat.c to audiod_command.c