CallStream: merge back from CallChannel the changes in remote member handling
CallStream: merge back from CallChannel the changes in remote member handling

The code that handles remote members in CallChannel was originally copied
from CallStream, but was modified a bit to fix some mistakes. This commit
merges back those changes to CallStream, so that the logic is identical.

detrout/telepathy-qt,TelepathyIM/telepathy-qt,TelepathyQt/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,anantkamath/telepathy-qt,detrout/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt,tiagosh/telepathy-qt,tiagosh/telepathy-qt,TelepathyIM/telepathy-qt,TelepathyIM/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt,TelepathyQt/telepathy-qt,TelepathyQt/telepathy-qt,special/telepathy-qt-upstream,anantkamath/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,TelepathyIM/telepathy-qt,detrout/telepathy-qt,tiagosh/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,TelepathyQt/telepathy-qt,special/telepathy-qt-upstream,freedesktop-unofficial-mirror/telepathy__telepathy-qt,tiagosh/telepathy-qt,special/telepathy-qt-upstream,TelepathyIM/telepathy-qt,anantkamath/telepathy-qt