DockerFile update for improvement (laradock#1568)

Docker file changes for image size improvements.

Author: valerianpereira

mysql/Dockerfile

@@ -9,9 +9,7 @@ LABEL maintainer="Mahmoud Zalt <mahmoud@zalt.me>"
 
 ARG TZ=UTC
 ENV TZ ${TZ}
-RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
-
-RUN chown -R mysql:root /var/lib/mysql/
+RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone && chown -R mysql:root /var/lib/mysql/
 
 COPY my.cnf /etc/mysql/conf.d/my.cnf