fix for exception while skipping system keyspace
fix for exception while skipping system keyspace

1)replace_key routine replacing all the matches of the skip_key
2)fix added to replace only the exact match

Change-Id: Id908f74d6f8e262d4b64c83fd01e7f98b14254fb
Closes-Bug: #1567067

Juniper/contrail-fabric-utils,Juniper/contrail-fabric-utils