cmd/go: make "finding" logging deterministic

In CL 204777, I made the "finding" messages in cachingRepo only print
after a “longish” delay, on the theory that they would help diagnose
slow or stuck fetches.

However, as I've been testing Go 1.14 beta 1, I've found that these
messages are mostly just noise, and the fact that they are so
nondeterministic causes both confusion and test flakes (#35539).

Moreover, it currently triggers once for each candidate module, when
what we're usually after is actually a specific package within the
module.

So let's log the package operation unconditionally instead of the
module fetches nondeterministically.

Fixes #35539
Updates #26152

Change-Id: I41a1c772465b2f0b357d3402bc372b6907773741
Reviewed-on: https://go-review.googlesource.com/c/go/+/213679


Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>