authz doesn't combine global and repository rules

As reported on users:

https://lists.apache.org/thread.html/1aef30b70b4063ecfa24f17be0e1c9998837b4f8b3f7e8b03de4e240@%3Cusers.subversion.apache.org%3E

The new 1.10 authz implementation doesn't correctly combine global rules such as [/foo] with repository rules such as [repo:/foo]. The result is that authz rules result grant less access in 1.10 than those same rules in 1.9.

Regression test added in https://svn.apache.org/r1835049