Revert "Add validation to KeyPair resource"

This reverts commit 6124fdea6552145ec38817bbd409b81d717be1c2.

Nova Keypair validation doesn't work with stack-update.  Validation will
fail even if the Nova Keypair resource wasn't changed.

Change-Id: Iaa17e97ca7847c344aabd46f62ae3068cfbbe061
Closes-Bug: #1296747
Merge "Revert "Add validation to KeyPair resource""