migration/rdma: Plug a memory leak and improve a message

migration/rdma: Plug a memory leak and improve a message

When migration capability @rdma-pin-all is true, but the server cannot
honor it, qemu_rdma_connect() calls macro ERROR(), then returns
success.

ERROR() sets an error.  Since qemu_rdma_connect() returns success, its
caller rdma_start_outgoing_migration() duly assumes @errp is still
clear.  The Error object leaks.

ERROR() additionally reports the situation to the user as an error:

    RDMA ERROR: Server cannot support pinning all memory. Will register memory dynamically.

Is this an error or not?  It actually isn't; we disable @rdma-pin-all
and carry on.  "Correcting" the user's configuration decisions that
way feels problematic, but that's a topic for another day.

Replace ERROR() by warn_report().  This plugs the memory leak, and
emits a clearer message to the user.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20230928132019.2544702-31-armbru@redhat.com>