get rhel7.3 selinux-policy-devel pkg for centos-7

Resolved conflict of bringing in this patch originally committed
to the 1.13.x branch. For this patch applied to the 1.12.x branch,
did not keep the photon case statement in generate.sh and did not
update to golang 1.7 in the centos-7/Dockerfile.

Signed-off-by: Andrew Hsu <andrewhsu@docker.com>

contrib/builder/rpm/amd64/centos-7/Dockerfile

@@ -7,6 +7,7 @@ FROM centos:7
 RUN yum groupinstall -y "Development Tools"
 RUN yum -y swap -- remove systemd-container systemd-container-libs -- install systemd systemd-libs
 RUN yum install -y btrfs-progs-devel device-mapper-devel glibc-static libseccomp-devel libselinux-devel libtool-ltdl-devel pkgconfig selinux-policy selinux-policy-devel sqlite-devel systemd-devel tar git
+RUN [ `rpm -q selinux-policy-devel | grep el7_3` ] || yum -y --enablerepo=cr install selinux-policy-devel
 
 ENV GO_VERSION 1.6.3
 RUN curl -fSL "https://storage.googleapis.com/golang/go${GO_VERSION}.linux-amd64.tar.gz" | tar xzC /usr/local

contrib/builder/rpm/amd64/generate.sh

@@ -132,6 +132,10 @@ for version in "${versions[@]}"; do
 			# use zypper
 			echo "RUN zypper --non-interactive install ${packages[*]}" >> "$version/Dockerfile"
 			;;
+		centos:7)
+			echo "RUN ${installer} install -y ${packages[*]}" >> "$version/Dockerfile"
+			echo 'RUN [ `rpm -q selinux-policy-devel | grep el7_3` ] || yum -y --enablerepo=cr install selinux-policy-devel' >> "$version/Dockerfile"
+			;;
 		*)
 			echo "RUN ${installer} install -y ${packages[*]}" >> "$version/Dockerfile"
 			;;