restapi: solve VCpuPin CNF exception in tests

Solve ClassNotFound exception in mapper tests related
to incorrect naming and lookup of VCpuPin class.
It also improves *MapperTest(s) runtime.

For example - VmMapperTest runs 12 seconds faster.

Change-Id: I9dfefff32fc764e09496bb742649fbba598022ac
Signed-off-by: Alissa Bonas <abonas@redhat.com>