Fix imap_pool hanging when getting a second MailBox (+stuff)

In the following situation:

- the pool has handed out one or more mailboxes already,
- if you'd call get_box(),
- imap_pool would hang.

the reason for this is that when you call get_box(), the pool checks if
all connections are still alive to prevent handing out dead ones. it'd
also check all boxes that were already handed out and in use, resulting
in hanging the thread and eventually deadlocking.

This commit:

- removes the list of handed out boxes from the alive check loop,
- removes commented out log messages that were present for finding this
  bug,
- adds a list where it'll track which threads are currently holding a
  mailbox.

0 files changed, 0 insertions, 0 deletions