Modify the beparams constants

Memory is renamed for easier use.

Reviewed-by: ultrotter

lib/constants.py

@@ -276,10 +276,16 @@ HVS_PARAMETERS = frozenset([
   ])
 
 # BE parameter names
-BE_MEMSIZE = "memory"
+BE_MEMORY = "memory"
 BE_VCPUS = "vcpus"
 BE_AUTOBALANCE = "auto_balance"
 
+BES_PARAMETERS = frozenset([
+  BE_MEMORY,
+  BE_VCPUS,
+  BE_AUTOBALANCE,
+  ])
+
 # BE GROUP
 BEGR_DEFAULT = "default"