client should not send requests with cxid=-4, -2, or -1

Once the cxid value increments to -4, the client will interpret the response as an auth packet rather than as a response to a request and will transparently drop the response and the request will hang.  Similarly, -2 will be seen as a ping and will be dropped hanging the request.  -1 shows up as a WatcherEvent and results in the error below.

2019-01-07T21:58:23.209+00:00 [INFO ] [main-SendThread(mnds1-2-phx.ops.sfdc.net:2181)] [ClientCnxn.java:1381] [:] - Session establishment complete on server mnds1-2-phx.ops.sfdc.net/10.246.244.71:2181, sessionid = 0x267859729d66320, negotiated timeout = 10000
2019-01-07T21:58:22.281+00:00 20190107215822.281000 [WARN ] [main-SendThread(mnds1-3-phx.ops.sfdc.net:2181)] [ClientCnxn.java:1235] [:] - Session 0x267859729d66320 for server mnds1-3-phx.ops.sfdc.net/10.246.244.69:2181, unexpected error, closing socket connection and attempting reconnect
java.io.IOException: Unreasonable length = 892612659
at org.apache.jute.BinaryInputArchive.checkLength(BinaryInputArchive.java:127) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]
at org.apache.jute.BinaryInputArchive.readString(BinaryInputArchive.java:81) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]
at org.apache.zookeeper.proto.WatcherEvent.deserialize(WatcherEvent.java:66) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]
at org.apache.zookeeper.ClientCnxn$SendThread.readResponse(ClientCnxn.java:839) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]
at org.apache.zookeeper.ClientCnxnSocketNIO.doIO(ClientCnxnSocketNIO.java:101) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]
at org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:363) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1214) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]