leapp upgrade: Fail with exit code 1 after errors
leapp upgrade: Fail with exit code 1 after errors

Previously, leapp upgrade would have return error code `0` even when
errors have been reported through the framework.

This change introduces the reporting of exit code `1` in case errors
have been reported.

Signed-off-by: Vinzenz Feenstra <600e8a10eeff4f08c65e2cf493cd851025e86fd2@redhat.com>

leapp-to/prototype,leapp-to/prototype,leapp-to/prototype,leapp-to/prototype