Add a routine to look up an elabinelab role.

tbsetup/ns2ir/tb_compat.tcl.in

 # -*- tcl -*-
 #
 # EMULAB-COPYRIGHT
-# Copyright (c) 2000-2011 University of Utah and the Flux Group.
+# Copyright (c) 2000-2012 University of Utah and the Flux Group.
 # All rights reserved.
 #
 
@@ -2054,6 +2054,22 @@ proc tb-set-elabinelab-role-attribute {role key value {order 0}} {
     }
 }
 
+proc tb-get-elabinelab-role-attribute {role key} {
+    var_import ::TBCOMPAT::EINEROLE;
+    var_import ::TBCOMPAT::EINEKEY;
+    var_import ::TBCOMPAT::EINEVALUE;
+    var_import ::TBCOMPAT::EINEORDER;
+    var_import ::TBCOMPAT::elabinelab_attributes;
+
+    set ret {}
+    set i [lsearch -glob $elabinelab_attributes "$role,$key,*,0"]
+    if {$i > -1} {
+	set values [split [lindex $elabinelab_attributes $i] ","]
+	set ret [lindex $values 2]
+    }
+    return $ret
+}
+
 proc tb-unset-elabinelab-role-attribute {role key} {
     var_import ::TBCOMPAT::EINEROLE;
     var_import ::TBCOMPAT::EINEKEY;