Send ChannelDialogController finish message on dismiss

NotificationInfo keeps track of whether or not it's presenting the
channel dialog editor, but was missing messages from the "tap outside"
dismissal of the dialog and would not present the dialog on subesquent
taps. This change makes the controller send the finish message on any
dismiss event

Fixes: 135484257
Test: atest ChannelEditorDialogControllerTest; visual
Change-Id: I25a124e4d875c146024a2051cd7c2e896d801c23