virsh.start: Add tests for starting long-named VM

This fix is a regression test for bug:
https://bugzilla.redhat.com/show_bug.cgi?id=1060557

Signed-off-by: Hao Liu <hliu@redhat.com>
Merge pull request #63 from Hao-Liu/fix_start

virsh.start: Add tests for starting long-named VM