Exclude firebird user from destruction

This user apparently has ~ set to /, and userdel fails.

No idea what this is. firebird -h reports "Firebird TCP/IP server
options are:".

sbin/seagl-reset-users

@@ -7,8 +7,8 @@ if ! [ $(id -u) == 0 ]; then
 	exit 1
 fi
 
-# Delete all existing users except root
-grep -v '^root' /etc/passwd | cut -d: -f1 | xargs -n 1 userdel -f -r
+# Delete all existing users except root (and firebird?? TODO what is this????)
+grep -ve '^root' -e '^firebird' /etc/passwd | cut -d: -f1 | xargs -n 1 userdel -f -r
 
 # Password hash corresponds to `password`
 adduser seagloperator -mp '$y$j9T$emVbho1jsDyzxlJVlATJU.$GYps0oI9FuW.WC3KCXZQkRDq8zGV0gjDIuJLAK1mtP8'