Users shouldn't be able to invoke scripts requiring AZ CLI if they cannot auth against it

[glennmusa]

What happens:

When invoking a Mission LZ script with a dependency on Azure CLI, I can do so from a terminal where my access has expired, but, Mission LZ scripts will continue to execute as if nothing is wrong and could put me into a weird state/confuse a user:

You'll notice mission LZ scripts continuing to try and execute Service Principal does not exist...creating despite not being able to get out and query that information to begin with.

Example:

> scripts/mlz_tf_setup.sh gmusadev eastus public
Verifying Service Principal is unique (sp-tf-mlz-gmusadev)
ERROR: AADSTS70043: The refresh token has expired or is invalid due to sign-in frequency checks by conditional access. The token was issued on 2021-02-17T15:42:34.0134674Z and the maximum allowed lifetime for this request is 43200.
Trace ID: [redacted]
Correlation ID: [redacted]
Timestamp: 2021-02-22 21:30:24Z
Service Principal does not exist...creating
ERROR: AADSTS70043: The refresh token has expired or is invalid due to sign-in frequency checks by conditional access. The token was issued on 2021-02-17T15:42:34.0134674Z and the maximum allowed lifetime for this request is 43200.
Trace ID: [redacted]
Correlation ID: [redacted]
Timestamp: 2021-02-22 21:30:25Z

What I expect to happen:
The script should fail gracefully and tell me to run az login

[brooke-hamilton]

This is a general issue -- deployment scripts should stop as soon as an error is encountered instead of continuing. The same problem happens if a required environment variable is missing.