Fix XML search for "privilege" elements in credentials.

The previous code searched for _all_ privileges, which returned
extraneous results in case of delegation.  We are now more precise
about the locations in the tree we're considering.

protogeni/lib/GeniCredential.pm.in

@@ -519,8 +519,9 @@ sub CreateFromSigned($$;$)
     bless($self, $class);
 
     # Dig out the capabilities
-    foreach my $cap (GeniXML::FindNodes('.//n:privileges/n:privilege',
-					 $root)->get_nodelist()) {
+    foreach my $cap (GeniXML::FindNodes('n:signed-credential/n:credential/' .
+					'n:privileges/n:privilege',
+					$root)->get_nodelist()) {
 	my $name = GeniXML::FindElement('n:name', $cap);
 	my $delegate = GeniXML::FindElement('n:can_delegate', $cap);
 	if (defined($name) && defined($delegate)) {