BUG 2970 : Throw a specific exception when schema validation fails

BUG 2970 : Throw a specific exception when schema validation fails

When resolving a modification if there is a failure in validating
a data node because it's schema is not present we should throw
a specific exception instead of just an IllegalArgument exception.

This specific exception can be used by CDS to determine if the failure
to add a node was due to a schema validation failure and then we will
attempt to prune data from the normalized node so that the invalid
data elements are removed.

Change-Id: Ieba347c29a9e92ea6aa7ccc2570935cd7a233b8e
Signed-off-by: Moiz Raja <moraja@cisco.com>