CLEANUP: server: rename server_find_by_name() to server_find()

CLEANUP: server: rename server_find_by_name() to server_find()

This function doesn't just look at the name but also the ID when the
argument starts with a '#'. So the name is not correct and explains
why this function is not always used when the name only is needed,
and why the list-based findserver() is used instead. So let's just
call the function "server_find()", and rename its generation-id based
cousin "server_find_unique()".