dashboard: more environment cleanups

sid was trying to use hg still.

And remove curl everywhere (except nacl). It's unnecessary.

Change-Id: I2a235d83b2bc7cf599c8de5796c724d8f368348e
Reviewed-on: https://go-review.googlesource.com/1368
Reviewed-by: David Symonds <dsymonds@golang.org>