Hygiene: Removing our custom phpunit config file

The core PHPUnit config seems to work better. I couldn't get any
MF tests to run with our config (without significantly changing it)
while they all seem to run successfully when using the core config.

Update `make phpunit` command for vagrant usage

Change-Id: Iab96d51949e8e316fb22473737147da2097b32ee
Merge "Hygiene: Removing our custom phpunit config file"