fix: remove underscores from cfg options in assoc array

Remove any possible underscores from the config options when creating
keys for the associative array used to look them up after capturing
environment variables.

This is a possible regression from fc0363a.

entrypoint.sh

@@ -10,10 +10,12 @@ readonly CONFIG_REGEX="^(\;|\#)?\ *([a-zA-Z_0-9]+)=.*"
 readarray -t existing_config_options < <(sed -En "s/$CONFIG_REGEX/\2/p" "$BARE_BONES_CONFIG_FILE")
 
 # Create an associative array for faster config option lookup
-declare -A config_from_uppercase
+declare -A option_for
 
 for config in "${existing_config_options[@]}"; do
-	config_from_uppercase["${config^^}"]="$config"
+	# Ignore underscores during lookup
+	no_underscores="${config//_/}"
+	option_for["${no_underscores^^}"]="$config"
 done
 
 # Grab the original command line that is supposed to start the Mumble server
@@ -63,7 +65,7 @@ else
 	while IFS='=' read -d '' -r var value; do
 		# Uppercase and remove underscores so MUMBLE_CONFIG_A_B == MUMBLE_CONFIG_AB
 		uppercase_variable="${var/MUMBLE_CONFIG_/}"
-		config_option="${config_from_uppercase[${uppercase_variable//_/}]}"
+		config_option="${option_for[${uppercase_variable//_/}]}"
 
 		if [[ -z "$config_option" ]]; then
 			>&2 echo "[ERROR]: Unable to find config corresponding to variable \"$var\""