Replaced github.com/bradfitz/http2 with the latest golang.org/x/net/http2
and updated the following dependencies:
golang.org/x/net @ a179abb31d787abdb406d922dff79635a8d784a4
golang.org/x/oauth2 @ 038cb4adce85ed41e285c2e7cc6221a92bfa44aa
google.golang.org/grpc @ 1684e4a49ba8e6c88a8628b26395f310a1e3d99f
Change-Id: Ic8f294f22a4ec7f7ee513fd1eb29a0b72ac41886