[2.2] add explicit profiler enabling, necessary on 2.2

[ricardclau]

Q	A
Doc fix?	yes
New docs?	no
Applies to	2.2+
Fixed tickets	None

In Symfony 2.2 you have to explicitly enable profiler in functional testing to inspect collected data.

This is covered in http://symfony.com/doc/current/cookbook/testing/profiling.html but I thought it would be better to have it documented also in this cookbook

[weaverryan]

Very nice catch and addition Ricard - thanks!

[ricardclau]

This should be merged into master as well, shouldn't it?

[wouterj]

@ricardclau that is done once in week by ryan, you don't need to create another PR.

[ricardclau]

Oh I was not aware about this workflow, thanks for clarifying 👍

[stof]

@ricardclau it is the same workflow than for the code :)