Failing BuildPlan generation with `--locked` does not return the cause of the error

[kayagokalp]

discovered at #2082 (comment).

If there is a dependency cycle, forc should not attempt to create the BuildPlan. Currently, after failing to create the BuildPlan from the lock file it also tries to create it from scratch.

[kayagokalp]

As it turns out this can be something more general,

When there is a problem with the BuildPlan generation from the lock file, (cyclic dependency is an example of this) and the user-provided --locked, we are not returning the problem that is coming from the BuildPlan generation. We only return the problem of --locked is provided while the lock file needs to be created.