jpackage tests fail when Desktop is not supported

If you run x86 configuration (cross-compiled on x86_64), then many tests would fail with:

$ CONF=linux-x86-server-fastdebug make images run-test TEST=tools/jpackage
...
can not load libgnomevfs-2.so
Exception in thread "main" java.lang.ExceptionInInitializerError
Caused by: java.lang.UnsupportedOperationException: Desktop API is not supported on the current platform
at java.desktop/java.awt.Desktop.getDesktop(Unknown Source)
at com.that/com.that.main.Florence.createInstance(Unknown Source)
at com.that/com.that.main.Florence.<clinit>(Unknown Source)
Failed to launch JVM
java.lang.AssertionError: Expected [0]. Actual [1]: Check command [/home/shade/trunks/jdk/build/linux-x86-server-fastdebug/test-support/jtreg_test_jdk_tools_jpackage/scratch/10/./testMainLauncherIsModular.ed4f638d/output/MainLauncherIsModularAddLauncherTest/bin/ModularAppLauncher](1) exited with 0 code

The tests probably need to check Desktop.isDesktopSupported(), similarly how they check GraphicsEnvironment.isHeadless().