Add unit tests for EchoInputMessageFactory, EchoReplyInputMessageFactory

Change-Id: I519e6cf4cb5657be3f506716c999da611079a1d6
Signed-off-by: Marian Adamjak <marian.adamjak@pantheon.sk>
Signed-off-by: Michal Polkorab <michal.polkorab@pantheon.sk>