fix(test): Correct unit test bugs

Return in mbuf_api_test.c was missing causing occasional
report of failed test when all tests passed.

unit_test.ksh wasn't properly searching for build directory
on systems which support lib64 naming conventions.

Change-Id: Idc208ef796c8dabf70c039e38fafab2a34db4df9
Signed-off-by: E. Scott Daniels <daniels@research.att.com>
diff --git a/test/mbuf_api_test.c b/test/mbuf_api_test.c
index fdc221a..796888f 100644
--- a/test/mbuf_api_test.c
+++ b/test/mbuf_api_test.c
@@ -102,4 +102,6 @@
 	} else {
 		fprintf( stderr, "<OK>	 mbuf_api tests pass\n" );
 	}
+
+	return errors;
 }