firmware: retain ordering in update servers

This only pertains to the connectivity audit changes from
26.1.8.  Treat the server from opnsense-update -M as the
primary one by not sorting the result.

PR: https://forum.opnsense.org/index.php?topic=52025.0

src/opnsense/scripts/firmware/hostnames.sh

@@ -60,4 +60,4 @@ for HOST in $( (for URL in ${URLS}; do
 	HOST=${URL#*://}
 	echo ${HOST%%/*}
 
-done) | sort -u); do echo ${HOST}; done
+done) | awk '!_[$0]++'); do echo ${HOST}; done