Ensure tests after the InstallCommand test will have a clean database.
Previous attempt failed because of a foreign key
Also, nightly on Travis seems to target PHP 7.2-dev, so I put 7.1 in requirement and moved nightly in allowed failures.
And it seems xdebug isn't shipped with PHP 7.1, so I added a workaround to avoid build to fail when trying to remove xdebug.ini file.
Instead of using a HTTP request we just login user like FOSUser does.
It allows us to mock service in container for functional tests.
Also, fix a bad config name in fos_user for firewall
And finally, add functional test to PocketImport
