Bugfix: msmtp logging

[papey]

Fixes a bug with msmtp logging by redirecting msmtp log to stdout and wraps the things into a dash script redirecting msmtp stdout to pid 1 stdout.

Testing procedure is listed below :

make 7.1-cli
docker container run --rm --name=msmtp-logging-test -t -i -e MAILS_DOMAIN="mail.example.com" -e MAILS_USER=user@example.com -e MAILS_HOST="mail.example.com" -e MAILS_FROM="from@example.com" -e MAILS_TOKEN="pass" bearstech/php-cli:7.1 bash
bash -c "echo "test" | sendmail dest@example.com

[papey]

@athoune merge if LGTY 👍

[papey]

More tests added, now can get logs from outside (ie docker daemon)