Deprecate reporting of local clock in circuit tests since a small number of users might have security problems with this.

node/IncomingPacket.cpp

@@ -1078,7 +1078,7 @@ bool IncomingPacket::_doCIRCUIT_TEST(const RuntimeEnvironment *RR,const SharedPt
 			Packet outp(originatorAddress,RR->identity.address(),Packet::VERB_CIRCUIT_TEST_REPORT);
 			outp.append((uint64_t)timestamp);
 			outp.append((uint64_t)testId);
-			outp.append((uint64_t)now);
+			outp.append((uint64_t)0); // field reserved for future use
 			outp.append((uint8_t)ZT_VENDOR_ZEROTIER);
 			outp.append((uint8_t)ZT_PROTO_VERSION);
 			outp.append((uint8_t)ZEROTIER_ONE_VERSION_MAJOR);

node/Packet.hpp

@@ -934,7 +934,7 @@ public:
 		 * Circuit test hop report:
 		 *   <[8] 64-bit timestamp (from original test)>
 		 *   <[8] 64-bit test ID (from original test)>
-		 *   <[8] 64-bit reporter timestamp (reporter's clock, 0 if unspec)>
+		 *   <[8] 64-bit reserved field (set to 0, currently unused)>
 		 *   <[1] 8-bit vendor ID (set to 0, currently unused)>
 		 *   <[1] 8-bit reporter protocol version>
 		 *   <[1] 8-bit reporter major version>