OPS-241 Ansible: MySql 5.6 installs should remove the 'test' database

Refactor installation of Python requirements.

The current code installs the Python requirements files in a different order
than "paver install_prereqs".  This has been causing problems for the
edx-solutions fork of edx-platform.

The code is also rather repetitive.  This patch cleans the code up a bit, while
at the same time making sure that the order in which the requirements files are
processed matches the order paver uses.

Additionally, the patch extends the list of requirements files which are scanned
for Github URLs by two items that seemed to be missing.

Update the apt-cache if it hasn't been updated within the last hour (…

Install python-mysqldb to allow ansible to run mysql tasks

Update the apt-cache if it hasn't been updated within the last hour (when installing system packages in edx_service)

Course discovery static files

[ECOM-3111] E-Commerce devstack uses wrong configuration

DEVOPS-3348 LTI component grade post back not working

Updates for recent repo requirements on base box (testeng).

Max/improve mongo status

Max/improve mongo rs member

Tweak python package versions to remove hardcoded os version and calculate it instead

Similar to the core ansible/abbey change made in
https://github.com/edx/configuration/commit/06153b69cf39e955b1c834f580cb96c000c70f4e

The packages are named trusty1 or precise1

Revert "E0d/ops 680a"

E0d/ops 680a