Create drupal/ dir before bootstrapping container contents

On a clean project, this directory will not exist when Docker image is build
for the first time. And this will trigger an Apache config checker warning
later in the script. Creating an empty directory will silence the warning in
the build output.

Dockerfile

@@ -3,6 +3,10 @@
 FROM    savoirfairelinux/lampd
 MAINTAINER Ernesto Rodriguez Ortiz <ernesto.rodriguezortiz@savoirfairelinuc.com>
 
+# Create project root directory and copy the structure
+RUN mkdir -p /opt/sfl/src/drupal
+COPY . /opt/sfl
+
 # Create user used by Drupalizer tasks
 RUN useradd --home-dir /opt/init --create-home drupalizer --shell /bin/bash && passwd -d drupalizer
 
@@ -24,10 +28,6 @@ fi\n\
 exec /bin/sh -c "$*"'\
 > /opt/init/init.sh && chmod a+x /opt/init/init.sh
 
-# Create project root directory and copy the structure
-RUN mkdir -p /opt/sfl
-COPY . /opt/sfl
-
 # Setup ssh keys to clone git repo
 RUN mv /opt/sfl/conf/id_rsa* /root/.ssh/
 RUN cat /root/.ssh/id_rsa.pub >> /root/.ssh/authorized_keys