In reviewing WT-6215 keith.smith noticed that there is overlap in parsing the configuration lines for backup information.

cursor/cur_backup_incr.c:curbackup_incr_blkmod and meta/meta_ckpt.c:ckpt_load_blk_mods have very similar parsing code paths.

These two functions have subtle differences. They compare against different strings and they fill in different data structures. A review of these function should be done to figure out a way to factor that out into one function.