fallocate fails in test environment

Functional test TestFile.testFileSizeLimit fails in test environment.
The test tries to allocate a space for several replicas of almost 5Gb file, to check the 5Gb limit.
This test will fail if the test environment has less than 3 * 5Gb of free space.
According to SAIO docs the test env is built with 1Gb volume which is obviously not enough.
From docs:
dd if=/dev/zero of=/srv/swift-disk bs=1024 count=0 seek=1000000
   (modify seek to make a larger or smaller partition)

Why this was working before? In my case it was working because VmWare engine prior to 5.0.0 build-812388 was blatantly ignoring fallocate as a noop.
But the problem has a bigger scope: after testFileSizeLimit fails, most of other tests also fail, they just don't have anough free space to run...

I.e. either we disable fallocate for the test duration or make test partition much bigger.