Disable performance playground

They playground isn't doing anything useful right now so there's no point in
running the tests. It generates extra mail and increases load times for the
graphs. Leaving the bash files around since it's likely these will be used in
the near future.
Merge pull request #820 from ronawho/disable-perf-playground

Disable performance playground

[reviewed by @thomasvandoren]

The playground isn't doing anything useful right now so there's no point in
running the tests. It generates extra mail and increases load times for the
graphs. Leaving the bash files around since it's likely these will be used in
the near future.