unit tests: vmmalloc_fork/ TEST1 and TEST3 (all/pmem/debug) hangs

[mramotowski]

Test hangs and never ends on Fedora24 with 4.8.10-200.fc24.x86_64 kernel.

[mramotowski]

Verified on 1.2-rc3-14-g06a5850

[mramotowski]

Now it hangs on ubuntu 16.04 with 4.8.10-040810-generic kernel.

[mramotowski]

And today also on Fedora24 with 4.8.10-200.fc24.x86_64 kernel.

[plebioda]

Look like there is an issue in the kernel. After running git bisect it looks like the following commit introduced this issue:

torvalds/linux@ac401cc