CORD-2545: Fix error in pure protobuf policies

Change-Id: Iedcec7ff63f4c5e29cbe4db281ce8d61ca82d5c9
diff --git a/lib/xos-genx/xosgenx/proto2xproto.py b/lib/xos-genx/xosgenx/proto2xproto.py
index f3acc23..d2bde67 100644
--- a/lib/xos-genx/xosgenx/proto2xproto.py
+++ b/lib/xos-genx/xosgenx/proto2xproto.py
@@ -97,7 +97,7 @@
                 rhs = rhs[1:-1]
 
             if rhs.startswith('policy:'):
-                str = rhs.split(':')[1]
+                str = rhs.split(':',1)[1]
                 val = self.fol_parser.parse(str, lexer = self.fol_lexer)
 
                 return m.PolicyDefinition(obj.name, val)