[Etherpad] Fix entrypoint

pica-etherpad/entrypoint.sh

@@ -22,7 +22,7 @@ if [ -z "${DB_HOST}" ]; then
 	exit 1
 fi
 
-while ! mysqladmin ping -u${DB_USER} -p${DB_PASSWORD} -h"${DB_HOST} &>/dev/null"; do
+while ! mysqladmin ping -u${DB_USER} -p${DB_PASSWORD} -h"${DB_HOST}" &>/dev/null; do
 		echo "Database server not ready yet, re-trying in 5 seconds..."
     sleep 5
 done