Add support to run Doctor test with more than one VM by setting
VM_COUNT to wanted amount of VMs. Normally half of those VMs
gets scheduled to host that is used for Doctor testing.
JIRA: DOCTOR-77
Change-Id: I9fac96c6f53c290fccc35a2fd933b9fb106b96f2 Signed-off-by: Tomi Juvonen <tomi.juvonen@nokia.com>