Remove unnecessary set_env_class_* Makefile targets
Remove unnecessary set_env_class_* Makefile targets

Now that the makefile is structured so that we always do `make <env>
<action>`, there's no need for the environment setup to be in separate
targets, it can be in the env targets themselves.

alphagov/paas-cf,jimconner/paas-cf,jimconner/paas-cf,alphagov/paas-cf,alphagov/paas-cf,jimconner/paas-cf,jimconner/paas-cf,alphagov/paas-cf,alphagov/paas-cf,jimconner/paas-cf,jimconner/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,jimconner/paas-cf