Increase metrics tool disk quota to 512M
Increase metrics tool disk quota to 512M

100M was not enough and causing staging failures. This started happening
after vendoring in more dependencies.

alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf