Do not run cobeginRace.chpl when doing memleaks testing.
Merge pull request #728 from vasslitvinov/skip-cobeginRace-for-memleaks

Do not run cobeginRace.chpl when doing memleaks testing.

Currently this test times out when running memory leak testing.
We decided not to run it there - see the thread on the internal list re
"parallel/cobegin/diten/cobeginRace regression".

Here is a summary.

Why does it time out?
* Memory leak testing currently runs on a virtual server, with qthreads.
* This test creates lots of tasks; at most 12 tasks are created at once.
* It runs a lot faster with guard pages disabled.
* So we conjecture that guard pages are very slow on that machine.

Can this test be made to succeed in this context? Yes, e.g.:
* turn off guard pages
* increase the timeout
* reduce the number of iterations
Re the last two... In 2008 this test ran quickly on computers that
were old back then - see commit 5bd5df6. So we want to keep the current
size and timeout in our other contexts.

Note also that this test currently does not generate memleaks info.
That's because it calls exit() (from ChapelBase.chpl), and that bypasses
the memleaks dump. And even if it didn't, we currently not do
any structured teardown upon exit(). So the memleaks report would be
very long, and not very useful.