Correct install script flaw when DBD_LIST is provided by the

build user.

This does not represent any significant change to the package,
and certainly not to the source code, so if people do not complain
about the discrepancy, then the -win32-src.zip package would include 
this fix.

Either way, it's not a regression so not a showstopper to 2.2.9.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@666353 13f79535-47bb-0310-9956-ffa450edef68