dm: free table mempools if not used in __bind

dm: free table mempools if not used in __bind

With request-based dm, the mempools don't need reloading when switching
tables, but the unused table mempools are not freed until the active
table is finally freed. Free them immediately if they are not needed.

Fixes: 29dec90a0f1d9 ("dm: fix bio_set allocation")
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Tested-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>