[varnishcache/varnish-cache] 7bb758: Ignore If-Modified-Since if we have If-None-Match

[Federico G. Schwindt]

  Branch: refs/heads/master
  Home:   https://github.com/varnishcache/varnish-cache
  Commit: 7bb758fd81265d912c28048d7a41c4316a8d8686
      https://github.com/varnishcache/varnish-cache/commit/7bb758fd81265d912c28048d7a41c4316a8d8686
  Author: Federico G. Schwindt <fgsch at lodoss.net>
  Date:   2015-12-12 (Sat, 12 Dec 2015)

  Changed paths:
    M bin/varnishd/cache/cache_rfc2616.c
    M bin/varnishtest/tests/c00026.vtc
    R bin/varnishtest/tests/r00907.vtc

  Log Message:
  -----------
  Ignore If-Modified-Since if we have If-None-Match

The latter takes precedence as per RFC 7232.  Also if we have an I-N-M
but no entity don't check I-M-S, just do a non-conditional request.