main/dhcp: fix vrf support

dhcrelay init.d overrides start(), due to this the built in vrf support
in openrc does not work. Due to this dhcrelay init.d must handle the
vrf support.
8 jobs for !14880 with dhcrelay-vrf in 9 minutes and 13 seconds (queued for 1 second)
latest detached
Status Job ID Name Coverage
  Lint
passed #417044
docker-alpine x86_64
lint

00:00:22

 
  Build
passed #417049
docker-alpine ci-build aarch64
build-aarch64

00:08:25

passed #417051
docker-alpine ci-build armhf
build-armhf

00:07:24

passed #417050
docker-alpine ci-build armv7
build-armv7

00:07:27

passed #417048
docker-alpine ci-build ppc64le
build-ppc64le

00:08:49

passed #417047
docker-alpine ci-build s390x
build-s390x

00:03:53

passed #417046
docker-alpine ci-build x86
build-x86

00:05:22

passed #417045
docker-alpine ci-build x86_64
build-x86_64

00:03:44