rename DIEGO_BETA -> DIEGO_STAGE_BETA [#80165358]

Signed-off-by: Joseph Palermo <jpalermo@pivotal.io>
set CF_DIEGO_STAGE_BETA explicitly [#80165358]

Signed-off-by: Joseph Palermo <jpalermo@pivotal.io>
test staging on DEA, running on Diego [#80165358]
s/restart/restage/ in migrating DEA-->Diego

[#80165358]
Cleanup unused assets
Finish the rename s/CF_DIEGO/DIEGO/g

Staging on Diego is now controlled by DIEGO_STAGE_BETA=true
Running on Diego is now controlled by DIEGO_RUN_BETA=true

[#80165358]

Signed-off-by: Johannes Petzold <jpetzold@pivotal.io>