ofproto-dpif-xlate: Fix bad memory free.
Clang reports possibly bad free of 'ofm' when it comes from the stack
instead of malloc because Clang is not able to verify whether the previous
if condition 'ctx->xin->xcache' still hold the same.  Fix it by
adding additional condition.
@@ -5131,7 +5131,7 @@ xlate_learn_action(struct xlate_ctx *ctx, const struct ofpact_learn *learn)
}
}
- if (ctx->xin->xcache) {
+ if (ofm != &ofm__) {
free(ofm);
}
