Adjust Dockerfile to end up in the right place while installing impor…

…ts and then running data val job (#81)

* Why we're CDing twice:

1. We need to be in app/ to install the dependencies
2. Then we need to be in app/src/ to run the script itself

* remove the double-move in the Dockerfile; I am going to cd into the appropriate location in telemetry-airflow to run the job instead

jobs/search-term-data-validation/Dockerfile

@@ -1,7 +1,7 @@
 FROM python:3
 MAINTAINER Chelsea Troy <ctroy@mozilla.com>
 
-WORKDIR /usr/app/src
+WORKDIR /usr/app/
 
 RUN pip install --upgrade pip
 COPY requirements.txt .