qemu_migration: Avoid mem.hard_limit > 0 check

My original commit v8.4.0-288-gf01fc4d119 accidentally forgot to fix
both instances of the same problem. While it fixed the destination side
of migration, the source one remained broken.

However, that commit was also wrong in saying the issue could have
caused unlimited memory locking to be allowed for QEMU when RDMA
migration was used. It could not, because the code would refuse to even
think about starting RDMA migration if hard_limit was not set. But
avoiding the "mem.hard_limit > 0" check is useful anyway.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_migration.c

@@ -4623,7 +4623,7 @@ qemuMigrationSrcStart(virDomainObj *vm,
     switch (spec->destType) {
     case MIGRATION_DEST_HOST:
         if (STREQ(spec->dest.host.protocol, "rdma") &&
-            vm->def->mem.hard_limit > 0 &&
+            virMemoryLimitIsSet(vm->def->mem.hard_limit) &&
             qemuDomainSetMaxMemLock(vm, vm->def->mem.hard_limit << 10,
                                     &priv->preMigrationMemlock) < 0) {
             return -1;