Bug 5485: Improve DataTreeModification pruning on recovery

Bug 5485: Improve DataTreeModification pruning on recovery

Modified the PruningDataTreeModification and NormalizedNodePruner to
validate path and node QNames via the SchemaContext instead of just
namespaces. This allows migration support for any element to be removed
from a yang hierarchy.

Also handled SchemaValidationFailedException on ready which can happen
with writes which don't immediately validate the sctructure as merge
does. The modification tree is re-applied with pruning.

Change-Id: I986d1116d2e25115f406abc21b1f816525387125
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>