Force the current directory to the server root in the invocation of the piped

logger processes.

Looking for confirmation from Rainer that this resolves the ambiguity
he observed in Message-ID: <4A0C9430.2090404@kippdata.de>.

Note that the shell may decide to ignore the chdir, so test with "|$cmd"
syntax to compare to the expected behavior from 5/14 or earlier. 


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@775327 13f79535-47bb-0310-9956-ffa450edef68