Revert 235333 "Pepper: Disable many flaky {TCP, UDP}Socket tests."

Fix has landed. Reenable the tests.

> Pepper: Disable many flaky {TCP, UDP}Socket tests.
> 
> I think that Yuzhu has a fix for this, but it's not checked in yet, and this
> contributed to all of ppapi_browsertests being turned off on linux aura.
> 
> BUG=316933
> R=dmichael@chromium.org
> 
> Review URL: https://codereview.chromium.org/61733024

TBR=teravest@chromium.org

Review URL: https://codereview.chromium.org/76533005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236057 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236057