Add host usb apis

Added the following api:

* GET api/hosts/[hostId]/hostusbs
* GET api/vms/[vmId]/hostusbs
* POST api/vms/[vmId]/hostusbs [HostUSB]
* DELETE api/vms/[vmId]/[devname]

Signed-off-by: walteryang47 <walteryang47@gmail.com>