Fixes 4826: prevent adding systems if env not yet created

[xbhouse]

Summary

• Checks if environment is created (rhsm_environment_created == true) before allowing user to assign the template to a system
• Displays an error if the environment has not been created but the template's update task has finished
• (You will see some unintended behavior here when adding multiple templates until this PR is merged)

Testing steps

Since this depends on Patch's API, this needs to be tested on stage (npm run start:stage). You will also need to have registered at least one system on stage. This also cannot be tested in ephemeral as the task that sets the rhsm_environment_created flag depends on candlepin.

1. Create a template and select Create template and add to systems to navigate to the AddSystemModal
2. Select a system. The Assign button should be disabled for a few seconds and have a tooltip. Once the template's update task has finished and the environment was created, the button should be enabled

[jlsherrill]

https://issues.redhat.com/browse/HMS-4826

[swadeley]

/retest

[xbhouse]

seeing something weird here, it seems like rhsm_environment_created doesn't stay true if the template sits for a while? if we try to assign a template to a system an hour or so after the template was created, its rhsm_environment_created value will be false after initially being set to true, so we won't be able to assign it unless we update the template. looking into it now.

EDIT: i was actually just creating or editing a template an hour or so after 😆 had nothing to do with the time. PR to fix that here

[Andrewgdewar]

Ack!

[swadeley]

/retest