Skip temp tables from basebackup.

Do not store temp tables in basebackup, they will not be visible anyway, so,
there are not reasons to store them.

Author: David Steel
Reviewed by: me
Discussion: https://www.postgresql.org/message-id/flat/5ea4d26a-a453-c1b7-eff9-5a3ef8f8aceb@pgmasters.net