revisiting disabling Linux32 testing

Last summer I posted a note requesting feedback regarding disabling tests on Linux32. To summarize, the feedback was

* We use Linux32 tests for sanity checking tests that aren't running on b2g 
* Linux64 tests don't have parity with the test coverage on Linux32
* Linux32 is a very small user base compared to Windows yet we allocate expensive resources to it. 
* Was mentioned that 25% of our contributor community run Linux, however it is unclear if this is Linux32 or Linux64
* Most people don't use our Linux32 builds, but rather the ones from their distro
* We do not have reliable telemetry numbers for Linux32 from distros for various reasons

https://groups.google.com/forum/#!searchin/mozilla.dev.planning/linux32/mozilla.dev.planning/wBgLRXCTlaw/-YzXkHxyBgAJ

I didn't proceed with the change at that time because of the test parity and b2g issues.  However, since that time we have disabled b2g builds and tests and achieved test parity on linux64.  Thus at this time, I'm looking to proceed to disable linux32 tests.

https://bugzilla.mozilla.org/show_bug.cgi?id=1209932


Kim
Mozilla Release Engineering