tests: Added POP3 graceful authentication cancellation tests
tests: Added SMTP graceful authentication cancellation tests
tests: Removed expected QUIT response from graceful cancellation tests

A failure during authentication, which is performed as part of the
CONNECT phrase (for IMAP, POP3 and SMTP) is considered by the multi-
interface as being closed prematurely (aka a dead connection). As such
these protocols cannot issue the relevant QUIT or LOGOUT command.

Temporarily fixed the test cases until we can fix this properly.