Reported by sharat87 in https://github.com/spaetz/offlineimap/pull/38,
he would often get an unhandled Exception when trying to
releaseconnection() a connection that was not in the pool of
connections.
The reason this could happen is that when folder.IMAP.quickchanged()
raises an Exception in select(), we would release the connection in the
"except" handling, and than release the same connection in the "finally"
clause, which led to the error. The right thing is to only release the
connection once, of course.
Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
61e754c65e