Flapping roster announcements for players in peer co-guild

[mrogaski]

If a player is experiencing frequent disconnects from the bridge channel, the gwComemberCache table is not updated to damp the announcements.

    "2014-10-22 21:11:34 -- [DEBUG/5] on_event: event=CHAT_MSG_CHANNEL_JOIN", -- [63]
    "2014-10-22 21:11:34 -- [DEBUG/5] chan_join: channel=6, player=Missanthropi-Sargeras", -- [64]
    "2014-10-22 21:11:34 -- [DEBUG/5] comember_cache: miss Missanthropi-Sargeras", -- [65]
    "2014-10-22 21:11:34 -- [DEBUG/5] Cp<ChatFrame1/SYSTEM, *, *>: |Hplayer:Missanthropi-Sargeras|h[Missanthropi-Sargeras]|h has come online.", -- [66]
    "2014-10-22 21:11:35 -- [DEBUG/5] on_event: event=CHAT_MSG_CHANNEL_LEAVE", -- [67]
    "2014-10-22 21:11:35 -- [DEBUG/5] chan_leave: channel=6, player=Missanthropi-Sargeras", -- [68]
    "2014-10-22 21:11:35 -- [DEBUG/5] comember_cache: miss Missanthropi-Sargeras", -- [69]
    "2014-10-22 21:11:35 -- [DEBUG/5] Cp<ChatFrame1/SYSTEM, *, *>: Missanthropi-Sargeras has gone offline.", -- [70]
    "2014-10-22 21:11:35 -- [DEBUG/5] on_event: event=CHAT_MSG_CHANNEL_JOIN", -- [71]
    "2014-10-22 21:11:35 -- [DEBUG/5] chan_join: channel=6, player=Missanthropi-Sargeras", -- [72]
    "2014-10-22 21:11:35 -- [DEBUG/5] comember_cache: miss Missanthropi-Sargeras", -- [73]
    "2014-10-22 21:11:35 -- [DEBUG/5] Cp<ChatFrame1/SYSTEM, *, *>: |Hplayer:Missanthropi-Sargeras|h[Missanthropi-Sargeras]|h has come online.", -- [74]