Description of problem:
When we invoke postConnect method we schedule a task which register a
channel in selector but in between we may close the channel due to
issues. This causes NPE which can be mitigated by checking actual state
of the channel.


Version-Release number of selected component (if applicable):


How reproducible:
Occasionly.

Steps to Reproduce:
Hard to reproduce.
Might happen in slow network and short heartbrat interval.

Additional info:
2015-12-21 18:21:41,230 INFO  [org.ovirt.engine.core.vdsbroker.PollVmStatsRefresher] (DefaultQuartzScheduler_Worker-3) [] Failed to fetch vms info for host 'buri05' - skipping VMs monitoring.
2015-12-21 18:21:41,229 ERROR [org.ovirt.engine.core.vdsbroker.HostMonitoring] (DefaultQuartzScheduler_Worker-58) [] Exception: org.ovirt.engine.core.vdsbroker.vdsbroker.VDSNetworkException: java.lang.NullPointerException
        at org.ovirt.engine.core.vdsbroker.vdsbroker.VdsBrokerCommand.createNetworkException(VdsBrokerCommand.java:157) [vdsbroker.jar:]
        at org.ovirt.engine.core.vdsbroker.vdsbroker.VdsBrokerCommand.executeVDSCommand(VdsBrokerCommand.java:120) [vdsbroker.jar:]
        at org.ovirt.engine.core.vdsbroker.VDSCommandBase.executeCommand(VDSCommandBase.java:65) [vdsbroker.jar:]
        at org.ovirt.engine.core.dal.VdcCommandBase.execute(VdcCommandBase.java:33) [dal.jar:]
        at org.ovirt.engine.core.vdsbroker.ResourceManager.runVdsCommand(ResourceManager.java:467) [vdsbroker.jar:]
        at org.ovirt.engine.core.vdsbroker.VdsManager.refreshCapabilities(VdsManager.java:634) [vdsbroker.jar:]
        at org.ovirt.engine.core.vdsbroker.HostMonitoring.refreshVdsRunTimeInfo(HostMonitoring.java:119) [vdsbroker.jar:]
        at org.ovirt.engine.core.vdsbroker.HostMonitoring.refresh(HostMonitoring.java:84) [vdsbroker.jar:]
        at org.ovirt.engine.core.vdsbroker.VdsManager.onTimer(VdsManager.java:226) [vdsbroker.jar:]
        at sun.reflect.GeneratedMethodAccessor22.invoke(Unknown Source) [:1.7.0_91]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.7.0_91]
        at java.lang.reflect.Method.invoke(Method.java:606) [rt.jar:1.7.0_91]
        at org.ovirt.engine.core.utils.timer.JobWrapper.invokeMethod(JobWrapper.java:81) [scheduler.jar:]
        at org.ovirt.engine.core.utils.timer.JobWrapper.execute(JobWrapper.java:52) [scheduler.jar:]
        at org.quartz.core.JobRunShell.run(JobRunShell.java:213) [quartz.jar:]
        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:557) [quartz.jar:]
Caused by: java.lang.NullPointerException
        at org.ovirt.vdsm.jsonrpc.client.reactors.SSLClient$2.call(SSLClient.java:137) [vdsm-jsonrpc-java-client.jar:]
        at org.ovirt.vdsm.jsonrpc.client.reactors.SSLClient$2.call(SSLClient.java:133) [vdsm-jsonrpc-java-client.jar:]
        at org.ovirt.vdsm.jsonrpc.client.utils.retry.Retryable.call(Retryable.java:27) [vdsm-jsonrpc-java-client.jar:]
        at java.util.concurrent.FutureTask.run(FutureTask.java:262) [rt.jar:1.7.0_91]
        at org.ovirt.vdsm.jsonrpc.client.utils.ReactorScheduler.performPendingOperations(ReactorScheduler.java:28) [vdsm-jsonrpc-java-client.jar:]
        at org.ovirt.vdsm.jsonrpc.client.reactors.Reactor.run(Reactor.java:61) [vdsm-jsonrpc-java-client.jar:]