Bug 3016 : This manual serialization of ImmutableList was done because in routed...

Bug 3016 : This manual serialization of ImmutableList was done because in routed rpc,
remote server was not able to deserialize the object in AKKA messages properly.
Following exception was thrown:

ERROR Remoting - cannot assign instance of com.google.common.collect.RegularImmutableList
to field org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.legacyPath of type
com.google.common.collect.ImmutableList in instance of org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier

Change-Id: I74daf7ab5a6d4c164bb87b1bebc5f4e2dffb8753
Signed-off-by: Harman Singh <harmasin@cisco.com>
(cherry picked from commit 63c9eb4f3bd1a50b6841bbfebb53c1443e5e6ff4)