Stop bundle/npm installing as root

Running NPM install as root was causing the pre-install hook to fail due
to the privilege drop. Additionally, the script wasn't actually in place
anyway compounding the sadness. Now we're switching to the docker user
for installing dependencies and copying the scripts directory into the
image first.

Change-Id: Ieaf38d9cd9947e7f809796e38340e10033ae1eb7
Reviewed-on: https://gerrit.instructure.com/101437
Tested-by: Jenkins
Product-Review: Caleb Guanzon <cguanzon@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Reviewed-by: Brad Horrocks <bhorrocks@instructure.com>

Dockerfile

@@ -31,14 +31,22 @@ RUN if [ -e /var/lib/gems/$RUBY_MAJOR.0/gems/bundler-* ]; then BUNDLER_INSTALL="
   && find $GEM_HOME ! -user docker | xargs chown docker:docker
 
 WORKDIR $APP_HOME
+
 USER root
 COPY Gemfile      ${APP_HOME}
 COPY Gemfile.d    ${APP_HOME}Gemfile.d
 COPY config       ${APP_HOME}config
 COPY gems         ${APP_HOME}gems
-RUN bundle install --jobs 8
+COPY script       ${APP_HOME}script
 COPY package.json ${APP_HOME}
+RUN chown -R docker:docker ${APP_HOME} /home/docker
+
+# Install deps as docker to avoid sadness w/ npm lifecycle hooks
+USER docker
+RUN bundle install --jobs 8
 RUN npm install
+USER root
+
 COPY . $APP_HOME
 RUN mkdir -p log \
             tmp \