Correctly exit sway on errors.

Calling `exit` in sway_terminate prevents sway from correctly shutting
down (freeing data, cleanly terminating the ipc server, etc.).

A better way is to exit straight away if the failure occurs before
`wlc_run` and use sway_abort as usual if it occur when wlc is running.

common/log.c

@@ -58,7 +58,7 @@ void sway_abort(const char *format, ...) {
 	vfprintf(stderr, format, args);
 	va_end(args);
 	fprintf(stderr, "\n");
-	sway_terminate();
+	sway_terminate(EXIT_FAILURE);
 }
 
 #ifndef NDEBUG