REGTESTS: map: check map_regm inside an ACL over an iterating fetch

REGTESTS: map: check map_regm inside an ACL over an iterating fetch

This test covers the bug fixed by this commit:

    7646c657a BUG/MEDIUM: map: do not overwrite the fetch context in pat_match_regm()

It uses map_regm in an ACL over req.hdr() with no occurrence. The first
value does not match, so the ACL runs a second iteration of the fetch,
which crashed the process before the fix. A request with two header
values checks that the fetch cursor survives the first iteration.

Thank you to @Michael-JRead for having produced the first version of this reg
test.

This must be backported with the fix above.