postfix: accept mynetworks as parameter
postfix: accept mynetworks as parameter

and rename mydestination paramter to match postfix module

SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site,SoftwareHeritage/puppet-swh-profile,SoftwareHeritage/puppet-swh-site