internal/lsp: fix minor bug in the PackageHandle function
internal/lsp: fix minor bug in the PackageHandle function

Test variants and test mains can result in multiple packages being
loaded for a single ID. Handle this case in the PackageHandle function
instead of returning an error.

Change-Id: Ic0024c5bded162a3e78a9cdcb9566449f3683e35
Reviewed-on: https://go-review.googlesource.com/c/tools/+/213457
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
Reviewed-by: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools