security/vault: improve rc.d script

• Add additional "monitor" command which throws statistics to stdout. For details, see https://www.vaultproject.io/docs/internals/telemetry.html
• Where possible, add additional "vault_syslog_output_*" rc vars to redirect stdout to syslog
• Add vault config to required files list
• Bump PORTREVISION to reflect package

PR: 215896
Submitted by: Pavel Timofeev <timp87@gmail.com> (with modifications)