ContainerManagementProtocolProxy modifies IPC timeout conf without making a copy

yarn-client's ContainerManagementProtocolProxy is updating ipc.client.connection.maxidletime in the conf passed in without making a copy of it. That modification "leaks" into other systems using the same conf and can cause them to setup RPC connections with a timeout of zero as well. relate to YARN-3497. This is a work around for tez running on 2.6 and 2.7.0 grids.