new CoordImportRobot.has_coord_qualifier() method

to check if the 'coordinates' property is already used as qualifier for
another claim and, in that case, avoid adding that property again.

also done some minor cleanup

bug: 65430
Change-Id: I0759cca01de15a6884708341e79cd3403b4af74e
Merge "new CoordImportRobot.has_coord_qualifier() method"