releng_common: multiple cors origins
releng_common: multiple cors origins

now it will be possibe to set multiple cors origins for the usecase when
we are proxying the backend on old domain.

andrei987/services,mozilla-releng/services,srfraser/services,andrei987/services,garbas/mozilla-releng-services,andrei987/services,lundjordan/services,mozilla-releng/services,andrei987/services,garbas/mozilla-releng-services,La0/mozilla-relengapi,lundjordan/services,La0/mozilla-relengapi,srfraser/services,garbas/mozilla-releng-services,garbas/mozilla-releng-services,srfraser/services,mozilla-releng/services,La0/mozilla-relengapi,lundjordan/services,mozilla-releng/services,srfraser/services,La0/mozilla-relengapi,lundjordan/services