DF-5684 FIX VALIDATION (patched kernel #1 with caps_priv_check_td(curthread, SYSCAP_NOQUOTA_WR))
--- as uid 1001 maxx:
$ vquota limit / 1; echo "maxx_setlimit_rc=$?"
send_command: vquotactl = -1
Failed to send message to kernel
maxx_setlimit_rc=1                      <- EPERM, no state change
--- as root (mount NOT crippled by the unpriv attempt):
$ echo patched >> /root/df5684.txt && echo ROOT_WRITE_OK_ON_PATCHED
ROOT_WRITE_OK_ON_PATCHED
--- regression, privileged use still works as root:
$ vquota limit / 1; echo root_setlimit_rc=$?
root_setlimit_rc=0
$ vquota show /
total: 0, limit = 1
$ vquota limit / 0 && echo root_limit_restored
root_limit_restored