Fix log output

[hannaeko]

Purpose

Fixes log messages not being redirected to log file when using starman.

Context

fixes #1013

Changes

• Don't duplicate the STDERR so log message are correctly redirected.
• Changes the default log level to info so that the default log level in RPCAPI is the same as the one in agent.
• Imports missing dependency.

How to test this PR

Start the RPCAPI:

unset ZM_BACKEND_RPCAPI_LOGLEVEL
starman --preload-app --error-log=/tmp/zm-rpcapi.log --pid=/tmp/zm-rpcapi.pid --listen=127.0.0.1:5000  script/zonemaster_backend_rpcapi.psgi

In another terminal start a new test:

./script/zmb start_domain_test --domain zonemaster.net

Only the pre-fork log messages should be displayed in STDERR:

2022-05-18T10:43:06Z [52630] [NOTICE] [Zonemaster::Backend::Config] Loading config: /tmp/zonemaster/backend_config.ini
2022-05-18T10:43:06Z [52630] [INFO] [Plack::Sandbox::_2fhome_2fgbm_2fworkspace_2fzonemaster_2fzonemaster_2dbackend_2fscript_2fzonemaster_backend_rpcapi_2epsgi] Enabling add_api_user method
2022-05-18T10:43:06Z [52630] [INFO] [Plack::Sandbox::_2fhome_2fgbm_2fworkspace_2fzonemaster_2fzonemaster_2dbackend_2fscript_2fzonemaster_backend_rpcapi_2epsgi] Enabling add_batch_job method

The file /tmp/zm-rpcapi.log should contain a line indicating the DB connection:

2022/05/18-12:39:12 Starman::Server (type Net::Server::PreFork) starting! pid(51380)
Binding to TCP port 5000 on host 127.0.0.1 with IPv4
Setting gid to "1000 1000 3 90 98 963 966 991 998 1000"
2022-05-18T10:39:15Z [51381] [NOTICE] [Zonemaster::Backend::DB] Connecting to database 'DBI:Pg:dbname=travis_zonemaster;host=10.10.86.42;port=5432' as user 'travis_zonemaster' Extra parameters: {'rpc_method' => 'start_domain_test'}

[ghost]

works as expected

[matsduf]

It looks fine, but I will test tomorrow, even if already merged.

[mattias-p]

LGTM