src/poky:bitbake: tests/fetch: support setting PV in the wget fetcher

Some code paths in latest_versionstring() need PV to be set correctly.

(Bitbake rev: 0a9f90ff658e09feda63b398ec35715a65ff6193)

Signed-off-by: Ross Burton <ross.burtonarm.com>
Signed-off-by: Richard Purdie <richard.purdielinuxfoundation.org>

Author: rossburton