Install fedora-gpg-keys for F27

The repo GPG keys moved into a separate package [1] which now needs to
be installed.

Since the fedora-release/fedora-repos split is *long* since over,
remove that work-around and add this one.

[1] https://pagure.io/fedora-repos/c/f69f3729511c3eba5f470b1d90ea2bfee372eb29?branch=f27

Change-Id: I9ad28d5bdb78375ae21dbb16e2d8c4effb32cb35

diskimage_builder/elements/yum-minimal/root.d/08-yum-chroot

@@ -72,10 +72,15 @@ function _install_repos {
     packages="basesystem filesystem setup "
 
     packages+="${DISTRO_NAME}-release "
-    # after fedora21, this is split into into a separate -repos
-    # package
-    if [ $DISTRO_NAME = fedora ]; then
-        packages+="${DISTRO_NAME}-repos "
+
+    # Starting in F21 this was split into a separate package
+    if [[ ${DISTRO_NAME} == 'fedora' ]]; then
+        packages+="fedora-repos "
+    fi
+
+    # F27 started putting gpg keys into this separate package
+    if [[ ${DISTRO_NAME} = fedora && ${DIB_RELEASE} -gt 26 ]]; then
+        packages+="fedora-gpg-keys "
     fi
 
     # By default, parent elements (fedora-minimal, centos-minimal)