aplay: avoid any further PCM writing if in abort

aplay: avoid any further PCM writing if in abort

Terminating stream with CTRL-C will set in_aborting flag which is used to leave any
write/read loop on the ALSA device.
After ending the read/write loop aplay tries to drain the stream which is not required and can also lead to malfunctions:
-If user interrupts a blocked/non responsive PCM (e.g. usb uac2 gadget which does not consume data
due to stream stopped by host) it will successfully terminate the write loop but will hang again in drain call.
This would require to hit CTRL-C again to unblock which should be avoided.
Aplay currently anyhow allows signal handler to get invoked only once.

Signed-off-by: Andreas Pape <apape@de.adit-jv.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>