Fix 'invalid argument' config error

Author: matyasselmeci

configs/60-osg-multiuser.cfg

@@ -1,7 +1,7 @@
 # Enable multiuser plugin. This makes XRootD to write the files with the
 # ownership of the user that authenticated to the server and not as the
 # 'xrootd' user
-if exec xrootd && defined ?~XC_ENABLE_MULTIUSER
+if defined ?~XC_ENABLE_MULTIUSER && exec xrootd 
   ofs.osslib ++ libXrdMultiuser.so
 else if defined ?~XC_ENABLE_MULTIUSER
   ofs.osslib libXrdMultiuser.so default