goimports will add an import for the package of target source file accidentally,
so check if package path is different from target source file when finding import candidates.
Fixesgolang/go#30663
Change-Id: I77c29bc74bef6c888e63ccb501b013a5fbc30b5c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/170238
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>