HBASE-8485 Retry to open a HLog on more exceptions

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1478880 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8487 Wrong description about regionservers in 2.4. Example configurations

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1478895 13f79535-47bb-0310-9956-ffa450edef68