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>