veyron/tools/mgmt/nminstall: add http download option.
veyron/tools/mgmt/nminstall: add http download option.

Change-Id: I50cccc3d6772c2ae1d00ce38edcb2999341b3355

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref