Prefix git suffixes with + instead of .

setuptools 8.0 enforces the accepted version of PEP440, which means
that 1.2.3.g123456 is now sorted before 1.0. Forget for a second that
under no obvious human inspection this makes sense, it is now the law of
the land and we must comply.

I swear to god I'm going to start coding in Go.

Change-Id: I2a5072d73e19ce77fa29ba5d8aa6e9649859a551
(cherry picked from commit fafd6c4db07789b2d378fdb5ceda89115d2abe30)