No-op modifications to file paths do not cause the file to be re-read

If a modification to a path parameter doesn't change the value but the contents have changed, an attempt to modify it to the current value does not cause it to be re-read. This makes it hard to force MaxScale to re-read a file from disk and it has to be worked around by renaming the file or by moving it elsewhere.

Treating all configuration modifications, even ones that do not change the actual values, as request to reapply any side-effects that might take place should fix this.