Merge pull request #768 in SNORT/snort3 from expected_leak to master

Merge pull request #768 in SNORT/snort3 from expected_leak to master

Squashed commit of the following:

commit bc95f17209177c4d6e1417bb5a80ba47ae831ac9
Author: Michael Altizer <mialtize@cisco.com>
Date:   Mon Jan 9 14:16:31 2017 -0500

    expected: Fix expected flow leak when expiring nodes during lookup

    If expected cache nodes are expired during lookup, their associated
    unconsumed flows are leaked, eventually leading to a segfault when the
    pool of expected flows are exhausted.  This fix releases the expected
    flows when expiring the expected node.

    Thanks to João Soares <joaosoares11@hotmail.com> for reporting the
    issue.