test: import file name for issue19028
test: import file name for issue19028

The pattern in NNN.dir directories is that if we have a.go,
the other files import "./a". For gc it happens to work to use a path,
but not for gofrontend. Better to be consistent.

Change-Id: I2e023cbf6bd115f9fb77427b097b0ff9b9992f17
Reviewed-on: https://go-review.googlesource.com/c/go/+/278113
Trust: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Than McIntosh <4b2922593166fc595a9b1a408f34f5d3817fe9d2@google.com>
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

golang/go,cloudflare/go,CAFxX/go,nawawi/go,nawawi/go,CAFxX/go,nawawi/go,CAFxX/go,CAFxX/go,cloudflare/go,golang/go,nawawi/go,golang/go,CAFxX/go,CAFxX/go,golang/go,cloudflare/go,cloudflare/go,cloudflare/go,nawawi/go,nawawi/go,CAFxX/go,golang/go,golang/go,cloudflare/go,cloudflare/go,nawawi/go,nawawi/go,golang/go,cloudflare/go,golang/go,CAFxX/go