zopewsgi: new --pidfile option

To write a pid file so that logrotate can send us signals. This is
still needed for neo storage for now.

See slapos!1395
4 jobs for fix/neo-logrotation
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-TestRunner1

00:32:57

passed ERP5.PerformanceTest-TestRunner1

00:26:43

failed ERP5.UnitTest-TestRunner1

01:14:00

running ERP5.UnitTest-Zope2-ForTestRunner1

13812:29:13