Switch from a LIST to TAILQ for the structure to store prefixes on a

Switch from a LIST to TAILQ for the structure to store prefixes on a
rib_entry. Mostly mechanical, this simplifies prefix_insert() and
prefix_remove() since the redo queue can now just use TAILQ_INSERT_TAIL().
rde_softreconfig_sync_reeval() needs to use TAILQ_CONCAT() to move
the list of prefixes over to the local TAILQ_HEAD to reapply them later.
OK tb@