Make mod_deflate skip compression if compression is enabled at SSL level.

Backport of r1359057 from trunk.

Submitted by: sf
Reviewed by: jorton, rjung
Backported by: rjung


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1364253 13f79535-47bb-0310-9956-ffa450edef68