Fix usage string for run_test.pl

git-svn-id: http://svn.osgeo.org/postgis/trunk@12022 b70326c6-7e19-0410-871a-916f4a2858ee
Print usage and exit if only option switches are given to run_test.pl

git-svn-id: http://svn.osgeo.org/postgis/trunk@12023 b70326c6-7e19-0410-871a-916f4a2858ee