Fix windows tests linked to slash separator

Tests reproduced on local windows 10 :

org.nuxeo.connect.update.standalone.registry.TestRollback.testHotfixUninstall
org.nuxeo.connect.update.standalone.registry.TestRollback.testUpgradeOnly1
org.nuxeo.connect.update.standalone.registry.TestRollback.testUpgradeOnly2
org.nuxeo.connect.update.standalone.registry.TestRollback.testUpgradeOnly3
org.nuxeo.connect.update.standalone.registry.TestRollback.testUpgradeOnly4
org.nuxeo.connect.update.standalone.registry.TestRollback.testUpgradeOnlyWithHotfixUninstall

org.nuxeo.ecm.core.io.transform.ExportAndTransformTest.testExportWithTransform

This ones are not reproduced on local windows 10, possibly a path size issue instead, but worth fixing anyway :

org.nuxeo.ecm.platform.pictures.tiles.service.test.TestService.testTilingSimple
org.nuxeo.ecm.platform.pictures.tiles.service.test.TestService.testTilingSpead
org.nuxeo.ecm.platform.pictures.tiles.service.test.TestService.testLazy
org.nuxeo.ecm.platform.pictures.tiles.service.test.TestService.testTilingWithShrink
org.nuxeo.ecm.platform.pictures.tiles.service.test.TestService.testTilingSimpleMagick
org.nuxeo.ecm.platform.pictures.tiles.service.test.TestService.testMagick
org.nuxeo.ecm.platform.pictures.tiles.service.test.TestService.testMagick2
org.nuxeo.ecm.platform.pictures.tiles.service.test.TestService.testGC
org.nuxeo.ecm.platform.pictures.tiles.service.test.TestService.testGC2