qemuxml2argvtest: Convert hugepages related tests to _CAPS_LATEST

qemuxml2argvtest: Convert hugepages related tests to _CAPS_LATEST

Currently, we have maybe a dozen tests for hugepages related
stuff in qemuxml2argvtest. In all cases DO_TEST() is used, which
means we have to enumerate all capabilities needed (though, it's
usually just QEMU_CAPS_OBJECT_MEMORY_RAM and
QEMU_CAPS_OBJECT_MEMORY_FILE, exceptionally
QEMU_CAPS_OBJECT_MEMORY_FILE_DISCARD too).

Instead of deleting the caps flags one-by-one, just switch the
tests to use DO_CAPS_LATEST().

The qemuxml2xmltest will undergo similar treatment in next
commit.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>