mainloop-test: Disarm io callback on EOF
Mainloop test uses io callback for PA_IO_EVENT_INPUT on stdin. With glib enabled PA_IO_EVENT_INPUT translates to glib G_IO_IN event which also matches descriptor in EOF state. While io callback does not check for EOF after reading from file descriptor this is causing mainloop-test to repeatedly read 0 bytes once EOF is reached, rearm defer callback and spam test log. Fix this by disarming io callback when EOF is reached in test run. Part-of: <!625>