mq: simplifies the refresh hint in checklocalchanges The `checklocalchanges` function in the `mq.queue` class takes a `refresh` argument that changes the error message of raised exception. When refresh is `True` the exception message is "local changes found, refresh first" otherwise, the message is just "local changes found". This changeset is the first of a series that extract `strip` into a standalone extension (as discussed in issue3824). This `checklocalchanges` function is indirectly used by the strip command. But in a standalone strip extension the concept of "refresh first" has no sense. In practice, When used in the context of the strip commands `refresh`'s value is always `False`. So my final goal is a be able to extract the `checklocalchanges` logic in a standalone extension but to keep the part related to "refresh first" in the mq extension. However the refresh handling is deeply entangled into the `checklocalchanges` code. It is handled as low a possible at the point we raise the exception. So we moves handling of refresh upper in the `checklocalchanges` code. This will allow the extraction of a simple version in the strip extension while mq can still inject its logic when needed. Two helper functions `localchangesfound` and `localchangedsubreposfound` died in the process they are replaced by simple raise lines.