HADOOP-1386.  Fix Path to not permit the empty string as a path, as this has lead to accidental file deletion.  Instead force applications to use '.' to name the default directory.  Contributed by Hairong.
HADOOP-1386.  Fix Path to not permit the empty string as a path, as this has lead to accidental file deletion.  Instead force applications to use '.' to name the default directory.  Contributed by Hairong.

git-svn-id: cd04eed87aeab77cae603320d37174dee2a0d977@540359 13f79535-47bb-0310-9956-ffa450edef68

optimizely/hbase,Shmuma/hbase-trunk,francisliu/hbase_namespace,Shmuma/hbase-trunk,jyates/hbase,optimizely/hbase,matteobertozzi/hbase,adragomir/hbaseindex,matteobertozzi/hbase,lichongxin/hbase-snapshot,jyates/hbase,cloudera/hbase,adragomir/hbaseindex,centiteo/hbase,StumbleUponArchive/hbase,StumbleUponArchive/hbase,jyates/hbase,matteobertozzi/hbase,bcopeland/hbase-thrift,bcopeland/hbase-thrift,StumbleUponArchive/hbase,lichongxin/hbase-snapshot,bcopeland/hbase-thrift,matteobertozzi/hbase,optimizely/hbase,francisliu/hbase_namespace,ryanobjc/hbase,jyates/hbase,francisliu/hbase_namespace,centiteo/hbase,Shmuma/hbase-trunk,cloudera/hbase,centiteo/hbase,ryanobjc/hbase,francisliu/hbase_namespace,Shmuma/hbase-trunk,jyates/hbase,StumbleUponArchive/hbase,bcopeland/hbase-thrift,lichongxin/hbase-snapshot,centiteo/hbase,Shmuma/hbase-trunk,lichongxin/hbase-snapshot,cloudera/hbase,matteobertozzi/hbase,francisliu/hbase_namespace,StumbleUponArchive/hbase,jyates/hbase,Shmuma/hbase-trunk,cloudera/hbase,adragomir/hbaseindex,jyates/hbase,francisliu/hbase_namespace,ryanobjc/hbase,StumbleUponArchive/hbase,jyates/hbase,centiteo/hbase,ryanobjc/hbase,bcopeland/hbase-thrift,matteobertozzi/hbase,adragomir/hbaseindex,centiteo/hbase,lichongxin/hbase-snapshot,adragomir/hbaseindex,ryanobjc/hbase,francisliu/hbase_namespace,adragomir/hbaseindex,matteobertozzi/hbase,francisliu/hbase_namespace,matteobertozzi/hbase,francisliu/hbase_namespace,jyates/hbase,Shmuma/hbase-trunk,bcopeland/hbase-thrift,cloudera/hbase,optimizely/hbase,adragomir/hbaseindex,StumbleUponArchive/hbase,lichongxin/hbase-snapshot,matteobertozzi/hbase,centiteo/hbase,optimizely/hbase,ryanobjc/hbase,bcopeland/hbase-thrift,optimizely/hbase,cloudera/hbase