hash/maphash: don't discard data on random seed init
Hash initializes seed on the first usage of seed or state with initSeed.
initSeed uses SetSeed which discards accumulated data.
This causes hash to return different sums for the same data in the first use
and after reset.
This CL fixes this issue by separating the seed set from data discard.
Fixes #37315
Change-Id: Ic7020702c2ce822eb700af462e37efab12f72054
GitHub-Last-Rev:
48b2f963e86c1b37d49b838a050cc4128bb01266
GitHub-Pull-Request: golang/go#37328
Reviewed-on: https://go-review.googlesource.com/c/go/+/220259
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>