man/vzctl.8: many fixes to --quiet/--verbose description

1. vzctl runscript can also accept flags.

2. Explain that flags can be used before any command.

3. Explain that these are only affecting console output,
   not file logging. In --quiet description it was incorrectly
   stated that it affects log file as well.

4. Note that scripts run by vzctl are still able to produce some output.

5. Explain where a default for --verbose comes from.

6. --verbose can be used multiple times.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
1 file changed