virt: Remove vcpucount_live() and fix vcpucount() in virsh.py

1. Remove vcpucount_live() and modify virsh vcpupin test file
2. Remove a unused parameter 'vcpu' in virsh vcpupin test file
   which was found by run_pylint.py
3. Add return value for vcpucount()

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>