[9fans] dnsdebug crash

[erik quanstrom]

another crash found:  on some architectures, it will crash in procsetname()
due to req.from being uninitialized.

- erik

/n/sources/plan9/sys/src/cmd/ndb/dnsdebug.c:323,328 - dnsdebug.c:315,321
                        l = &(*l)->next;
                        continue;
                }
+               memset(&req, 0, sizeof req);
                req.isslave = 1;
                req.aborttime = NS2MS(nowns) + Maxreqtm;
                *l = dnresolve(rp->host->name, Cin, Ta, &req, 0, 0, Recurse, 0, 
0);