`mc mirror --watch` should exit with non-zero status code on failure

[jadolg]

Expected behavior

When any error occurs during the mirror operation, mc should exit with a non-zero status code instead of just logging the error and continuing.

Actual behavior

mc logs the errors but continues to run.

Steps to reproduce the behavior

Try anything that would cause a problem like non existing bucket in the destination.

mc --version

mc version RELEASE.2025-02-15T10-36-16Z (commit-id=383560b1c3d6912042e8c8c275bb78e83e67ef2b)
Runtime: go1.23.6 linux/amd64

System information

Ubuntu 22.04
5.15.0-122-generic

[jadolg]

I think changing monitorMirrorStatus to use fatalIf instead of errorIf should solve this. This probably breaks the --retry flag though.