server crashes on incorrect operation type

[Dmitry Simonenko]

no check is made for u32 op to be in valid range:

box_process_rw(struct txn *txn, Port *port,
77 u32 op, struct tbuf *data)
78 {
79 ev_tstamp start = ev_now(), stop;
80
81 stat_collect(stat_base, op, 1);
82
83 @try {
84 Request *request = [[Request build: op] init: data];
85 [request execute: txn :port];
(gdb) l
86 txn_commit(txn);
87 }
88 @catch (id e) {
89 txn_rollback(txn);
90 @throw;
91 }

[Dmitry Simonenko (pmwkaa)]

fix pushed on the branch bug1009992