Implement '+' plus operator in noderange

+ operator generates an 'end node' from the nodename to the left
and adding the specified value to the number at the end.  This is
as restrictive as the xCAT 2.x perl implementation to ensure best
compatibility.

confluent_server/confluent/noderange.py

@@ -126,7 +126,6 @@ class NodeRange(object):
         if self.cfm.is_node(entname):
             return set([entname])
         if self.cfm.is_nodegroup(entname):
-            nodes = set([])
             grpcfg = self.cfm.get_nodegroup_attributes(entname)
             nodes = grpcfg['nodes']
             if 'noderange' in grpcfg and grpcfg['noderange']:
@@ -171,7 +170,24 @@ class NodeRange(object):
                 raise Exception('Verification configmanager required')
             return set(self.cfm.filter_nodenames(nameexpression, filternodes))
         elif '+' in element:
-            raise Exception('TODO: plus range')
+            element, increment = element.split('+')
+            try:
+                nodename, domain = element.split('.')
+            except ValueError:
+                nodename = element
+                domain = ''
+            increment = int(increment)
+            elembits = _numextractor.parseString(nodename).asList()
+            endnum = str(int(elembits[-1]) + increment)
+            left = ''.join(elembits)
+            if domain:
+                left += '.' + domain
+            right = ''.join(elembits[:-1])
+            right += endnum
+            if domain:
+                right += '.' + domain
+            nrange = left + ':' + right
+            return self.expandrange(nrange, ':')
         if self.cfm is None:
             return set([element])
         raise Exception(element + ' not a recognized node, group, or alias')