dropping incomplete indexes (Issue #337).

trx_rollback_or_clean_recovered(ibool all): New function, split from
trx_rollback_or_clean_all_recovered().  all==FALSE will only roll back
dictionary transactions.

recv_recovery_from_checkpoint_finish(): Call
trx_rollback_or_clean_recovered(FALSE) before
row_merge_drop_temp_indexes().

rb://158 approved by Sunny Bains