max number of open files when testing HBase on the Jenkins server

[Mikhail Bautin]

Hello,

I saw this error when testing my patch on Jenkins:

Caused by: java.io.IOException: Too many open files
        at sun.nio.ch.IOUtil.initPipe(Native Method)
        at sun.nio.ch.EPollSelectorImpl.<init>(EPollSelectorImpl.java:49)
        at 
sun.nio.ch.EPollSelectorProvider.openSelector(EPollSelectorProvider.java:18)
        at java.nio.channels.Selector.open(Selector.java:209)
        at 
org.apache.zookeeper.ClientCnxnSocketNIO.<init>(ClientCnxnSocketNIO.java:42)
        at sun.reflect.GeneratedConstructorAccessor40.newInstance(Unknown 
Source)
        at 
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at java.lang.Class.newInstance0(Class.java:355)
        at java.lang.Class.newInstance(Class.java:308)
        at 
org.apache.zookeeper.ZooKeeper.getClientCnxnSocket(ZooKeeper.java:1737)
        ... 55 more

(Full log: 
https://builds.apache.org/job/PreCommit-HBASE-Build/364//testReport/org.apache.hadoop.hbase.client/TestAdmin/testCheckHBaseAvailableClosesConnection/)

I am not sure who maintains the Jenkins server, but it would be nice to
increase the maximum number of open files for HBase unit tests.

Thanks,
--Mikhail