Fix failure on TestDublinCoreStorage.testCopyDocument on MariaDB

see https://qa2.nuxeo.org/jenkins/view/8.10/job/8.10/job/nuxeo-8.10-fullbuild-multidb-linux-norandom/287/Slave=MULTIDB_LINUX_810,dbprofile=mariadb,jdk=java-8-oracle/testReport/org.nuxeo.ecm.platform.dublincore/TestDublinCoreStorage/testCopyDocument/

• Stacktrace

  java.lang.AssertionError: expected:<java.util.GregorianCalendar[time=1504591357000,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Etc/UTC",offset=0,dstSavings=0,useDaylight=false,transitions=0,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2017,MONTH=8,WEEK_OF_YEAR=36,WEEK_OF_MONTH=2,DAY_OF_MONTH=5,DAY_OF_YEAR=248,DAY_OF_WEEK=3,DAY_OF_WEEK_IN_MONTH=1,AM_PM=0,HOUR=6,HOUR_OF_DAY=6,MINUTE=2,SECOND=37,MILLISECOND=0,ZONE_OFFSET=0,DST_OFFSET=0]> but was:<java.util.GregorianCalendar[time=1504591356000,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Etc/UTC",offset=0,dstSavings=0,useDaylight=false,transitions=0,lastRule=null],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2017,MONTH=8,WEEK_OF_YEAR=36,WEEK_OF_MONTH=2,DAY_OF_MONTH=5,DAY_OF_YEAR=248,DAY_OF_WEEK=3,DAY_OF_WEEK_IN_MONTH=1,AM_PM=0,HOUR=6,HOUR_OF_DAY=6,MINUTE=2,SECOND=36,MILLISECOND=0,ZONE_OFFSET=0,DST_OFFSET=0]>