[__hostname] Extend os switches with RedHat-derivatives (CentOS, Fedora, RedHat, Scientific)

cdist/conf/type/__hostname/explorer/persistent_hostname

@@ -37,7 +37,7 @@ in
 	suse)
 		[ -f /etc/HOSTNAME ] && cat /etc/HOSTNAME
 		;;
-	scientific|centos)
+	centos|fedora|redhat|scientific)
 		[ -f /etc/sysconfig/network ] && awk -F= '/^HOSTNAME=/ { print $2 }' /etc/sysconfig/network
 		;;
 	freebsd)

cdist/conf/type/__hostname/gencode-remote

@@ -58,12 +58,12 @@ EOF
 fi
 
 # Use the good old way to set the hostname. Also if hostnamectl fails.
-case "$os" in
-    archlinux|debian|ubuntu|devuan|centos|coreos|alpine)
+case $os in
+    archlinux|debian|ubuntu|devuan|coreos|alpine)
         printf "printf '%%s\\\\n' '$name_should' > /etc/hostname\\n"
         echo "hostname -F /etc/hostname"
     ;;
-    freebsd|openbsd)
+    centos|fedora|redhat|scientific|freebsd|openbsd)
         # NOTE: Writing the hostname to file is done in the manifest.
         echo "hostname '$name_should'"
     ;;

cdist/conf/type/__hostname/manifest

@@ -46,7 +46,7 @@ case "$os" in
         # handled in gencode-remote
         :
     ;;
-    scientific|centos)
+    centos|fedora|redhat|scientific)
         __key_value sysconfig-hostname \
             --file /etc/sysconfig/network \
             --delimiter '=' \