Code review comment for lp:~sergei.glushchenko/percona-xtrabackup/20-bug856400

Introduced/moved code that had compilation warnings and should be addressed:

xtrabackup.cc: In function ‘ulint rm_if_not_found(const char*, const char*, const char*, void*)’:
xtrabackup.cc:6383: warning: unused variable ‘space’ [-Wunused-variable]

Other than the warning, the fix seems reasonable, I like the use of the fn pointer to try to keep the code reasonably factored.

One minor thing is that around diff line 346, if xtrabackup_apply_deltas fails, inc_dir_tables_hash is not freed.