[Etherpad] Fix environment name in entrypoint

pica-etherpad/entrypoint.sh

 #!/usr/bin/env bash
 set -e
 
-if [ -z "${ETHERPAD_ADMIN_PASSWORD}" ]; then
-	echo >&2 'Error : missing required ${ETHERPAD_ADMIN_PASSWORD} environment variable, exiting.'
+if [ -z "${ADMIN_PASSWORD}" ]; then
+	echo >&2 'Error : missing required ${ADMIN_PASSWORD} environment variable, exiting.'
 	exit 1
 fi
-if [ -z "${ETHERPAD_DB_NAME}" ]; then
-	echo >&2 'Error : missing required ${ETHERPAD_DB_NAME} environment variable, exiting.'
+if [ -z "${DB_NAME}" ]; then
+	echo >&2 'Error : missing required ${DB_NAME} environment variable, exiting.'
 	exit 1
 fi
-if [ -z "${ETHERPAD_DB_USER}" ]; then
-	echo >&2 'Error : missing required ${ETHERPAD_DB_USER} environment variable, exiting.'
+if [ -z "${DB_USER}" ]; then
+	echo >&2 'Error : missing required ${DB_USER} environment variable, exiting.'
 	exit 1
 fi
-if [ -z "${ETHERPAD_DB_PASSWORD}" ]; then
-	echo >&2 'Error : missing required ${ETHERPAD_DB_PASSWORD} environment variable, exiting.'
+if [ -z "${DB_PASSWORD}" ]; then
+	echo >&2 'Error : missing required ${DB_PASSWORD} environment variable, exiting.'
 	exit 1
 fi
-if [ -z "${ETHERPAD_DB_HOST}" ]; then
-	echo >&2 'Error : missing required ${ETHERPAD_DB_HOST} environment variable, exiting.'
+if [ -z "${DB_HOST}" ]; then
+	echo >&2 'Error : missing required ${DB_HOST} environment variable, exiting.'
 	exit 1
 fi
 
-while ! mysqladmin ping -u${ETHERPAD_DB_USER} -p${ETHERPAD_DB_PASSWORD} -h"${ETHERPAD_DB_HOST}"; do
+while ! mysqladmin ping -u${DB_USER} -p${DB_PASSWORD} -h"${DB_HOST}"; do
     sleep 1
 done
 
 # Check if database already exists
-RESULT=`mysql -u${ETHERPAD_DB_USER} -p${ETHERPAD_DB_PASSWORD} \
-	-h${ETHERPAD_DB_HOST} --skip-column-names \
-	-e "SHOW DATABASES LIKE '${ETHERPAD_DB_NAME}'"`
+RESULT=`mysql -u${DB_USER} -p${DB_PASSWORD} \
+	-h${DB_HOST} --skip-column-names \
+	-e "SHOW DATABASES LIKE '${DB_NAME}'"`
 
-if [ "$RESULT" != $ETHERPAD_DB_NAME ]; then
+if [ "$RESULT" != $DB_NAME ]; then
 	# mysql database does not exist, create it
-	echo "Creating database ${ETHERPAD_DB_NAME}"
+	echo "Creating database ${DB_NAME}"
 
-	mysql -u${ETHERPAD_DB_USER} -p${ETHERPAD_DB_PASSWORD} -h${ETHERPAD_DB_HOST} \
-	      -e "create database ${ETHERPAD_DB_NAME}"
+	mysql -u${DB_USER} -p${DB_PASSWORD} -h${DB_HOST} \
+	      -e "create database ${DB_NAME}"
 fi
 
 exec "$@"