[IOT-3140] Fix roles deinit crash

Change-Id: I27bab5b348a4b0c52319447ce52e9ebdf3755628
Signed-off-by: Aleksey Volkov <a.volkov@samsung.com>

resource/csdk/security/src/rolesresource.c

@@ -1093,6 +1093,7 @@ OCStackResult DeInitRolesResource(void)
     FreeSymmetricRolesList(gSymmetricRoles);
 
     gRoles = NULL;
+    gSymmetricRoles = NULL;
 
     return res;
 }