qemu-char: Set foo_tag = 0 when returning FALSE from callbacks

qemu-char: Set foo_tag = 0 when returning FALSE from callbacks

While reviewing some patches I found this problem where tcp_chr_accept
does not clear listen_tag when returning FALSE, leading to a double
g_source_remove of the underlying source. Not really a problem unless the id
gets re-used in between, but still something we should fix.

While at it I've also reviewed all the other code in qemu-char.c for
similar problems and found that pty_chr_timer has the same problem.

Cc: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Message-id: 1366890782-10311-1-git-send-email-hdegoede@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>