Increase client idle and connection timeouts to reduce network load

These changes were introduced in d5a151a in 0.3.1.1.

Maybe we should:

• revert the changes, or increase the values
• make consensus parameters for them

+/** If we haven't yet decided on a good timeout value for circuit
+ * building, we close idle circuits aggressively so we can get more
+ * data points. */
+#define IDLE_TIMEOUT_WHILE_LEARNING (1*60)

-/** If we haven't yet decided on a good timeout value for circuit
- * building, we close idles circuits aggressively so we can get more
- * data points. */
-#define IDLE_TIMEOUT_WHILE_LEARNING (10*60)

+#define CONNTIMEOUT_CLIENTS_BASE 180 // 3 to 4.5 min
+    timeout = CONNTIMEOUT_CLIENTS_BASE
+        + crypto_rand_int(CONNTIMEOUT_CLIENTS_BASE/2);