CA-101571: Allow the vcpu params weight and cap value to be set independently

Issue: If only one of the weight and cpu is set, then a Not_found error is raised and a None is returned because of which the param set is not propagated further.

Fix: Two separate try with blocks have been put for weight and cap each which when not set returns its respective default value.

Signed-off-by: Ravi Pandey <ravi.pandey@citrix.com>