Strip leading and trailing hyphens

Strip leading and trailing hyphens in the resulting munged hostname.
Leading and trailing hyphens are not valid according to RFCs 952 and 1123.
(This problem surfaces immediately when using the default configuration of
OneFlow, since it names new VMs ending with a parenthesis.)

base_arch/etc/one-context.d/05-hostname

@@ -20,7 +20,7 @@ function get_dns_name() {
 }
 
 if [ -n "$SET_HOSTNAME" ]; then
-    set_hostname $(echo "$SET_HOSTNAME" | sed -e 's/[^-a-zA-Z0-9]/-/g')
+    set_hostname $(echo "$SET_HOSTNAME" | sed -e 's/[^-a-zA-Z0-9]/-/g' -e 's/^-*//g' -e 's/-*$//g')
 elif [ -n "$DNS_HOSTNAME" ]; then
     set_hostname $(get_dns_name)
 fi

base_deb.one/etc/one-context.d/05-hostname

@@ -22,7 +22,7 @@ function get_dns_name() {
 }
 
 if [ -n "$SET_HOSTNAME" ]; then
-    set_hostname $(echo "$SET_HOSTNAME" | sed -e 's/[^-a-zA-Z0-9]/-/g')
+    set_hostname $(echo "$SET_HOSTNAME" | sed -e 's/[^-a-zA-Z0-9]/-/g' -e 's/^-*//g' -e 's/-*$//g')
 elif [ -n "$DNS_HOSTNAME" ]; then
     set_hostname $(get_dns_name)
 fi

base_rpm.one/etc/one-context.d/05-hostname

@@ -23,7 +23,7 @@ function get_dns_name() {
 }
 
 if [ -n "$SET_HOSTNAME" ]; then
-    set_hostname $(echo "$SET_HOSTNAME" | sed -e 's/[^-a-zA-Z0-9]/-/g')
+    set_hostname $(echo "$SET_HOSTNAME" | sed -e 's/[^-a-zA-Z0-9]/-/g' -e 's/^-*//g' -e 's/-*$//g')
 elif [ -n "$DNS_HOSTNAME" ]; then
     set_hostname $(get_dns_name)
 fi