Propagate $ENABLE_INTROSPECTION environment variable passthough to the planb-tokeninfo fix

[smirnov]

Enable passthrough of environment variable ENABLE_INTROSPECTION to the planb upstart job and startup script.

[jbspeakr]

seems to work with TaupageStaging-AMI-20180323-150822. close?

[jbspeakr]

wait. this looks weird:

• in the taupage setup the variable tokeninfo_enable_introspection get's written into meta.
• but in tokeninfo init it expects tokeninfo_introspection to be present in meta.

I would expect introspection not to work anymore after a reboot. also those inconsistencies make it really hard to figure out what to use. please make it consistent to our current docs.

[jbspeakr]

also it would be nice to have a consistent naming schema for related config:
local_planb_tokeninfo: true together with tokeninfo_introspection: true is not nice.

I would prefer something like local_planb_tokeninfo: trueand local_planb_tokeninfo_introspection: true

let's fix this and adapt our docs.

[smirnov]

The second instance of propagation (in the setup script, it's needed to propagate secret-vars.sh overlay) can be dropped altogether and just be kept in the upstart init script (then this setting will require to be set explicitly in senza.yaml).