KVM Test: Add qmp_command test.

This script have coverd following qmp command:
query-hpet, query-kvm, query-mice, query-status
query-name, query-uuid, query-version, query-chardev
query-blockstats, memsave, pmemsave, query-cpus
cpu, query-vnc, query-block, query-commands
query-balloon, balloon, cont, stop
and a negative test with wrong command.

This script will check result by following way:
cmd_result_check = equal, will compare cmd_return_value with qmp command output.
cmd_result_check = contain, will try to find cmd_return_value in qmp command output.
cmd_result_check = m_equal_q, will compare key value in monitor command output and qmp command output.
cmd_result_check = m_in_q, will try to find monitor command output's key value in qmp command output.
cmd_result_check = post_contain, will try to find cmd_return_value in post command output.

This update is base on upstream QMP patchset.

Changes from v1:
Bug fix and update according to ldoktor's comment

Signed-off-by: Feng Yang <fyang@redhat.com>
KVM-test: Add format check for qmp_command test
Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu.tests.cfg: Add config for qmp_command.py test script.

Signed-off-by: Feng Yang <fyang@redhat.com>
qemu.tests: Make qmp_command suitable for more host

List some case only Host_RHEL.6
Do not run these case in RHEL3, RHEL4 guest.
Reconfig qmp_query-mice test case.
Rename qmp_device_add to qmp_redhat_device_add.
Re-design qmp_command.qmp_query-version test case

Signed-off-by: Feng Yang <fyang@redhat.com>