Redmine#6331: Skip non-empty directories silently when recursively deleting.

(cherry picked from commit 3eb20427fb9c1b303466aad08008a9195afc4f5d)

Conflicts:
	cf-agent/verify_files_utils.c
Merge pull request #2049 from jimis/3.6.x

Redmine#6331: Skip non-empty directories silently when recursively deleting
Merge remote-tracking branch 'upstream/3.6.x' into 3.6.x_surfsara