virttest.libvirt_xml: Add class for cputune entry

1) Use a dedicated class VMCPUTune to manipulate `<cputune>` tag
   instead of using a tag string and a lot of attributes which is
   not intuitive when using.

2) Add a simple getter setter delter unittest for this class.

3) Fixed two `<string> is not <string>` to `<string> != <string>`.
   The first one is identity test and will not alway get `False`
   even if two strings are equal.

Signed-off-by: Hao Liu <hliu@redhat.com>
virttest.test_setup: Change os.system to utils.system_output.

Command may could not finsih in some host, which make our test loop
hang. So change os.system to utils.system_output with timeout set.

Signed-off-by: Feng Yang <fyang@redhat.com>
utils_misc: Use re.split to do regexp split

The .split() method of python's standard string type does not take a
regexp as an argument, only another string. Switch to re.split().

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
Fix the ping4 function

Signed-off-by: Yanbing Du <ydu@redhat.com>
backends.libguestfs: No need param other_tests_dirs anymore.

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
Merge pull request #1572 from yumingfei/libguestfs_fix

Backends: Libguestfs fix
virttest.qemu_storage: PEP8 Fix
virttest.remote: PEP8 Fix
virttest.utils_libguestfs: PEP8 Fix
Merge pull request #1567 from zqad/fixes

utils_misc: Use re.split to do regexp split
Merge pull request #1571 from will-Do/ping_fix

Fix the ping4 function
Merge pull request #1565 from FengYang/system

virttest.test_setup: Change os.system to utils.system_output.
Merge pull request #1563 from Hao-Liu/fix_schedinfo

virttest.libvirt_xml: Add class for cputune entry
virttest.libvirt_xml.vm_xml: PEP8 Fixes