cmd/go: fix selection of packages for testing Currently it works incorrectly if user specifies own build tags and with race detection (e.g. runtime/race is not selected, because it contains only test files with +build race).
cmd/go: fix selection of packages for testing
Currently it works incorrectly if user specifies own build tags
and with race detection (e.g. runtime/race is not selected,
because it contains only test files with +build race).

R=golang-dev, r
CC=golang-dev
http://codereview.appspot.com/6814107

apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,tv42/old-go,apparentlymart/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,dsriram/golang,gnanderson/go,pombredanne/go-deleteme,dsriram/golang,apparentlymart/golang,gnanderson/go,gnanderson/go,gnanderson/go,tv42/old-go,dsriram/golang,dsriram/golang,apparentlymart/golang,apparentlymart/golang,dsriram/golang,tv42/old-go,gnanderson/go,pombredanne/go-deleteme,gnanderson/go,tv42/old-go,dsriram/golang,gnanderson/go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,apparentlymart/golang