ai: any hostile unit != any hostile diplomat.
Freeciv 3.0 has hostile enabler controlled actions that aren't diplomatic.
The function is_city_surrounded_by_our_spies() is used when the Diplomat/Spy
control code checks if a new Diplomat/Spy is needed.
Stop assuming that any unit capable of performing any hostile action is
capable of performing a hostile Spy/Diplomat action in the function
is_city_surrounded_by_our_spies().
See bug #25272
git-svn-id: svn://svn.gna.org/svn/freeciv/trunk@34448 a0f10bec-cc02-0410-94fc-a9cfff90b4cd