virttest.standalone_test: Use name instead shortname in print_guest_list

When we list the guest names with run we need the whole guest name but not
the shortname. Otherwise we will filter more cases than expect when we use
the output from --list-guests to run a test.

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
Merge pull request #1454 from ypu/guestname

virttest.standalone_test: Use name instead shortname in print_guest_list