Fix an error spotted by sparse.

Without the parens, the 2 first bits are reseted, instead of just the one for CONDFLAG_NOCASE.

This "bug" looks harmless as the first bit (CONDFLAG_NONE) is never tested.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1697735 13f79535-47bb-0310-9956-ffa450edef68