init.d/hostname: Document checkbashism false positive.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

init.d/hostname.in

@@ -10,7 +10,9 @@ depend() {
 
 start()
 {
-	hostname=${hostname-${HOSTNAME-localhost}}
+	# HOSTNAME variable used to be defined in caps in conf.d/hostname. 
+	# It is also a magic variable in bash.
+	hostname=${hostname-${HOSTNAME-localhost}} # checkbashisms: false positive
 	ebegin "Setting hostname to $hostname"
 	hostname "$hostname"
 	eend $? "Failed to set the hostname"