qemu.tests.balloon_check: Make memory ballooning cases works for windows guests

Make the free memory check command configurable.

changes from v1:
  - Add the Windows guest memory judge code as the value get from
    windows should charge with different method.

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu.tests.balloon_check: Add error context to this script

This test script has no error context and test step, this patch adds
them, and update some logging message.

Changes from V2:
 * Update docstring and error context message.

Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
qemu.tests.balloon_check: Fix bug that global name 'cur_mem' is not defined

Signed-off-by: Feng Yang <fyang@redhat.com>
qemu.tests.balloon_check: Check memory status after sub tests

Confirm the memory status after sub tests from both monitor and
inside guests.

changes from v1:
  - error message update

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu.tests.balloon_check: Update the related params for balloon_check

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu.tests.balloon_check: Improve the script

This patch mainly does following improvements:

Update the method to check memory from check different ways
for different OS to check the memory change in the test which may
works for both Windows and Linux.

Add a param to check if run sub test to make the operation of
separate evict and enlarge cases easier.

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu.tests.balloon_check: Separate enlarge and evict cases

Update the related new parameters and separated the enlarge and evict
cases

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu.tests.balloon_disable: Add a subtest: ballon_disable

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu.tests.balloon_disable: Make balloon_disable could work with qmp monitor.

Signed-off-by: Feng Yang <fyang@redhat.com>
qemu.tests: Add test case balloon check qmp

In the kernel above 2.6.34, info balloon support more detail
messages. This case use to check if the output of info balloon
is suitable our expect.

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu.tests: Indentation fixes

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>