Ubdate base images to CentOS 8 Stream

PR k8snetworkplumbingwg#223 updated base images to CentOS 8 which is EOL now so we can't
build new images using it.

Closes: k8snetworkplumbingwg#238

Dockerfile

@@ -3,7 +3,7 @@ WORKDIR /go/src/github.com/k8snetworkplumbingwg/sriov-network-operator
 COPY . .
 RUN make _build-manager BIN_PATH=build/_output/cmd
 
-FROM centos:8
+FROM quay.io/centos/centos:stream8
 COPY --from=builder /go/src/github.com/k8snetworkplumbingwg/sriov-network-operator/build/_output/cmd/manager /usr/bin/sriov-network-operator
 COPY bindata /bindata
 ENV OPERATOR_NAME=sriov-network-operator

Dockerfile.sriov-network-config-daemon

@@ -4,7 +4,7 @@ COPY . .
 RUN make _build-sriov-network-config-daemon BIN_PATH=build/_output/cmd
 RUN make plugins BIN_PATH=build/_output/pkg
 
-FROM centos:8
+FROM quay.io/centos/centos:stream8
 ARG MSTFLINT=mstflint
 RUN yum -y update && ARCH_DEP_PKGS=$(if [ "$(uname -m)" != "s390x" ]; then echo -n ${MSTFLINT} ; fi) && yum -y install hwdata $ARCH_DEP_PKGS && yum clean all
 LABEL io.k8s.display-name="sriov-network-config-daemon" \

Dockerfile.webhook

@@ -3,7 +3,7 @@ WORKDIR /go/src/github.com/k8snetworkplumbingwg/sriov-network-operator
 COPY . .
 RUN make _build-webhook BIN_PATH=build/_output/cmd
 
-FROM centos:8
+FROM quay.io/centos/centos:stream8
 LABEL io.k8s.display-name="sriov-network-webhook" \
       io.k8s.description="This is an admission controller webhook that mutates and validates customer resources of sriov network operator."
 COPY --from=builder /go/src/github.com/k8snetworkplumbingwg/sriov-network-operator/build/_output/cmd/webhook /usr/bin/webhook