CLOUDSTACK-2683: DevCloud systemVMs fail to launch

DevCloud is a XCP Kronos based xen. For this we use the XcpOssResource
whose memory limits were not set explicitly. Instead the base
CitrixResourceBase would set the limits. static_min was set to 128MB
failing the cpvm and ssvm start fails whose offerings have 100MB set to
the max limits.

Signed-off-by: Prasanna Santhanam <tsp@apache.org>
agent: Only probe running VMs for the current Hypervisor Type

Otherwise we try to probe for LXC VMs on a KVM hypervisor and vise versa.