Continue trying to remove NFS directory on temporary errors for up to a minute.
The previous async removal process breaks in the following case during VictoriaMetrics start
- VictoriaMetrics opens index, finds incomplete merge transactions and starts replaying them.
- The transaction instructs removing old directories for parts, which were already merged into bigger part.
- VictoriaMetrics removes these directories, but their removal is delayed due to NFS errors.
- VictoriaMetrics scans partition directory after all the incomplete merge transactions are finished
and finds directories, which should be removed, but weren't still removed due to NFS errors.
- VictoriaMetrics panics when it finds unexpected empty directory.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/162
Do not give up after 11 attempts of directory removal on laggy NFS.
Add `vm_nfs_dir_remove_failed_attempts_total` metric for counting the number of failed attempts
on directory removal.
Log failed attempts on directory removal after long sleep times.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/162
Unremoved directories may lead to inconsistent data directory,
so VictoriaMetrics will fail to start next time.
So panic on the first error when trying to remove directory in order
to simplify recover process.
