Fix TestDefaultImporterServiceWithMeta on MySQL / MariaDB

org.nuxeo.ecm.core.api.DocumentNotFoundException: /default-domain/workspaces/import-src-with-metadata
	at org.nuxeo.ecm.core.storage.sql.coremodel.SQLSession.resolvePath(SQLSession.java:196)
	at org.nuxeo.ecm.core.api.AbstractSession.resolveReference(AbstractSession.java:348)
	at org.nuxeo.ecm.core.api.AbstractSession.getDocument(AbstractSession.java:953)
	at org.nuxeo.ecm.platform.importer.tests.TestDefaultImporterServiceWithMeta.testImporterContribution(TestDefaultImporterServiceWithMeta.java:66)

org.nuxeo.ecm.core.api.DocumentNotFoundException: /default-domain/workspaces/import-src/hello.pdf
	at org.nuxeo.ecm.core.storage.sql.coremodel.SQLSession.resolvePath(SQLSession.java:196)
	at org.nuxeo.ecm.core.api.AbstractSession.resolveReference(AbstractSession.java:348)
	at org.nuxeo.ecm.core.api.AbstractSession.getDocument(AbstractSession.java:953)
	at org.nuxeo.ecm.platform.importer.tests.TestImportWithMeta.testMDImport(TestImportWithMeta.java:75)