Avoid leaking ping_timer in MainChannelClient
Avoid leaking ping_timer in MainChannelClient

This leaks happen for every connection. Potentially the timer can
be called after the client is closed causing an use after free.
Recently RED_STATISTICS was switched off by default but previous
version have this issue.

Signed-off-by: Frediano Ziglio <55d48b080b2e443e395cde84d2c83b135a4ff48e@redhat.com>
Acked-by: Pavel Grunt <fbda40b445316123f12a5a6bd7556918ea74f4bc@redhat.com>

fgouget/spice,fgouget/spice,fgouget/spice,fgouget/spice