BUG/MEDIUM: patterns: previous fix was incomplete

Dmitry Sivachenko <trtrmitya@gmail.com> reported that commit 315ec42
("BUG/MEDIUM: pattern: don't load more than once a pattern list.")
relies on an uninitialised variable in the stack. While it used to
work fine during the tests, if the uninitialized variable is non-null,
some patterns may be aggregated if loaded multiple times, resulting in
slower processing, which was the original issue it tried to address.

The fix needs to be backported to 1.5.
BUG/MEDIUM: payload: ensure that a request channel is available

Denys Fedoryshchenko reported a segfault when using certain
sample fetch functions in the "tcp-request connection" rulesets
despite the warnings. This is because some tests for the existence
of the channel were missing.

The fetches which were fixed are :
  - req.ssl_hello_type
  - rep.ssl_hello_type
  - req.ssl_sni

This fix must be backported to 1.5.