Use go 1.5.1 on concourse
Use go 1.5.1 on concourse

* go 1.4.3 does not support 1.5.1-style ldflags

[#107504580]

Signed-off-by: Stephen Levine <72d5489bdb659bea8b15ba0173fe796f11329883@pivotal.io>

cloudfoundry-incubator/lattice-ci,cloudfoundry-incubator/lattice-ci,cloudfoundry-incubator/lattice-ci