blob: do not call statvfs() if EBLOB_NO_FREE_SPACE_CHECK is set
blob: allow eblob to init with very long paths

Problem was with stat_file being only 256 bytes long
blob: lock database on start

This will prevent multiple instances of libeblob from working with
single database.

Reported by: isharov@
ci: remove EBLOB_NO_FREE_SPACE_CHECK from second run