package yum: stop to install epel-release explicitly

It should be installed via groonga-release. If it's not installed, we
should fix groonga-release.

packages/yum/build-rpm.sh

@@ -64,13 +64,17 @@ run cp /vagrant/tmp/${distribution}/*.spec rpmbuild/SPECS/
 
 package_name=$(cd rpmbuild/SPECS; echo *.spec | sed -e 's/\.spec$//g')
 
-run yum install -y epel-release
 case ${distribution} in
   fedora)
     USE_MYSQLSERVICES_COMPAT=yes
     run yum install -y mariadb-devel
     ;;
   centos)
+    release_rpm=groonga-release-1.2.0-1.noarch.rpm
+    wget http://packages.groonga.org/${distribution}/${release_rpm}
+    run rpm -U ${release_rpm}
+    rm -f ${release_rpm}
+
     case ${package_name} in
       mysql55-${PACKAGE})
 	USE_MYSQLSERVICES_COMPAT=yes
@@ -112,12 +116,6 @@ case ${distribution} in
         fi
         ;;
     esac
-
-    release_rpm=groonga-release-1.2.0-1.noarch.rpm
-    wget http://packages.groonga.org/${distribution}/${release_rpm}
-    run rpm -U ${release_rpm}
-    rm -f ${release_rpm}
-    run yum makecache
     ;;
 esac
 run yum install -y ${DEPENDED_PACKAGES}