[PATCH] TagCheck reports an identical warning multiple times after viewing validator preferences

[mrwojo]

With r5210

Repro:

1. Create a simple way tagged highway=service and barrier=wall.
2. Validate. You should see a warning: "barrier used on a way - Suspicious tag/value combinations (1)".
3. Open JOSM's Preferences dialog. Open the Validator settings page. Just press OK.
4. Validate. The number of warnings has incremented: "barrier used on a way - Suspicious tag/value combinations (2)". The single problematic way is being reported twice with an identical warning.

TagCheck.initializeData() is called once on startup and when the user presses "OK" on the Validator Preferences dialog. checkerData (and a few other static lists) is appended to every time initializeData() is called, but it's never reset anywhere, so checks are added redundantly without bound.

[mrwojo]

initializeData: clear the static lists first

[simon04]

In 5270/josm:

fix #7745 - TagCheck reports an identical warning multiple times after viewing validator preferences (patch by mrwojo)