Also use it for errors that were otherwise silently dropped
This makes it much easier to debug problems.
Also added command line control over whether the rpc trace messages are printed, which allows you to read the
log, otherwise the file edit messages swamp the log.
Change-Id: I7b70fd18034a87b2964e6d6d5f6f33dcaf7d8ea8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/170178
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
