tests.kdump: Add new sub test for multiple guests

define some functions for kdump, maybe other case
can reuse these functions late.

Signed-off-by: Shuping Cui <scui@redhat.com>
qemu.test: Update the check method in smbios_table

In the machine_type check for smbios_table, we only care the main version
information but not the details. And the command line output from guest
will include more than the version info:
System.Version mismatch, Set 'RHEL 7.0.0 PC'
but guest is : 'RHEL 7.0.0 PC (i440FX + PIIX, 1996)'

So update the check method for it.

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
Merge pull request #1349 from ypu/smbios_table

qemu.test: Update the check method in smbios_table
Merge pull request #1305 from spcui/kdump

tests.kdump: Add new sub test for multiple guests
qemu: Fix vhost params behavior.

when param[vhost]= [on, force] it create vhost-fds and pass it to
qemu vm correct way.

Signed-off-by: Jiří Župka <jzupka@redhat.com>