Breaks heroku ps:exec

[msiebuhr]

When using the new heroku ps:exec-feature to SSH into a running dyno, no environment variables are set, so when the scripts in profile.d/ is sourced, the shell exits without getting to the interactive login.

> heroku ps:exec --app foobar
Establishing credentials... done
Connecting to web.1 on ⬢ foobar...
DATADOG_API_KEY environment variable not set. Run: heroku config:add DATADOG_API_KEY=<your API key>%
>

Patch at tactileentertainment@a07f98a :

> heroku ps:exec --app foobar
Establishing credentials... done
Connecting to web.1 on ⬢ foobar...
DATADOG_API_KEY environment variable not set. Run: heroku config:add DATADOG_API_KEY=<your API key>
DATADOG_HOST_NAME nor HEROKU_APP_NAME environment variable set. Run: heroku apps:info|grep ===|cut -d' ' -f2
Some required keys are missing, not starting the agent.
~ $