Fix memory leak if unit test fails

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/test_suite_lmots.function b/tests/suites/test_suite_lmots.function
index 53ab02f..fd6a89f 100644
--- a/tests/suites/test_suite_lmots.function
+++ b/tests/suites/test_suite_lmots.function
@@ -193,6 +193,7 @@
 
 exit:
     mbedtls_lmots_public_free( &ctx );
+    mbedtls_free( exported_pub_key );
 }
 /* END_CASE */