nginx-util: fix PROVIDES and issue #6905

nginx-ssl-util and nginx-ssl-util-nopcre are replacements for each other,
but cannot replace nginx-util (instead conflict with it).

The hard coded [::1] could lead to a nginx error if build without IPv6.
So, get the loopback addresses dynamically.

Signed-off-by: Peter Stadler <peter.stadler@student.uibk.ac.at>