Also changed name from TestUnix... to TestUnixgram....

Updates #21965

Change-Id: I2833110b77e9fe1b28d4a15feb3d70453ab98d3b
Reviewed-on: https://go-review.googlesource.com/66333
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>
Reviewed-by: Rob Pike <r@golang.org>