[Libguestfs] [PATCH] tests: Increase appliance memory when testing 256+ disks.

[Richard W.M. Jones]

Currently the tests fail on x86 with recent kernels:

  FAIL: test-255-disks.sh

This confused me for a while because our other test program
(utils/max-disks/max-disks.pl) reports that it should be possible to
add 255 disks.

Well it turns out that the default amount of appliance memory is
sufficient if you're just adding disks, but if you try to add _and_
partition those disks there's insufficient memory and the daemon falls
over with an out of memory error.

I considered increasing the default appliance memory, and this is
certainly one way to fix the problem.  However this penalises every
user for what is a fairly niche use case.  This takes an alternative
approach of increasing the appliance memory for the affected tests.

Related links:

  https://bugzilla.redhat.com/show_bug.cgi?id=1478201
  https://rwmj.wordpress.com/2017/04/28/how-many-disks-can-you-add-to-a-virtual-linux-machine-contd/

Rich.