Fixing user directory creation order

Dockerfile

@@ -23,10 +23,10 @@ RUN dpkg --add-architecture i386 && \
 
 # SET STEAM USER
 RUN useradd -d /app -m steam
-RUN mkdir /app/server && mkdir /app/steamcmd
-
 USER steam
+
 WORKDIR /app
+RUN mkdir /app/server && mkdir /app/steamcmd
 
 # INSTALL STEAMCMD
 RUN wget -P /tmp/ https://steamcdn-a.akamaihd.net/client/installer/steamcmd_linux.tar.gz \