patch 8.0.1628: channel log doesn't mention exiting

Problem:    Channel log doesn't mention exiting.
Solution:   Add a ch_log() call in getout().

src/main.c

@@ -1389,6 +1389,9 @@ getout(int exitval)
     win_T	*wp;
 
     exiting = TRUE;
+#if defined(FEAT_JOB_CHANNEL)
+    ch_log(NULL, "Exiting...");
+#endif
 
     /* When running in Ex mode an error causes us to exit with a non-zero exit
      * code.  POSIX requires this, although it's not 100% clear from the