Added positive path Signature validation test

Added signature validation test cases infrastructre and
positive path test case for verify function.

Change-Id: I0e02a07b726ed08757a21b97871154622534c989
Signed-off-by: Jayanth Othayoth <ojayanth@in.ibm.com>
diff --git a/test/Makefile.am b/test/Makefile.am
index 5b30065..6dcba30 100755
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -35,4 +35,5 @@
 	$(top_builddir)/openpower_update_manager-watch.o \
 	$(top_builddir)/openpower_update_manager-item_updater.o \
 	$(top_builddir)/org/openbmc/Associations/openpower_update_manager-server.o \
+	$(top_builddir)/image_verify.cpp \
 	-lstdc++fs