try auto fix improper config on shark client launch.

some hadoop default config may make shark does not work properly. for example: property "mapreduce.framework.name" default value is "local", which would lead to a shark error while run query sql, because hive compiler take it as a local task and generate the file path based on local file system.
the error is:java.lang.IllegalArgumentException: Wrong FS: file:/tmp/root/hive_2014-01-20_15-03-01_857_5999805006588400427/_tmp.-ext-10001, expected: hdfs://localhost:9000
        at org.apache.hadoop.fs.FileSystem.checkPath(FileSystem.java:642)
        at org.apache.hadoop.hdfs.DistributedFileSystem.getPathName(DistributedFileSystem.java:181)
        at org.apache.hadoop.hdfs.DistributedFileSystem.access$000(DistributedFileSystem.java:92)
        at org.apache.hadoop.hdfs.DistributedFileSystem$17.doCall(DistributedFileSystem.java:1106)
        at org.apache.hadoop.hdfs.DistributedFileSystem$17.doCall(DistributedFileSystem.java:1102)
        at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
        at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1102)
        at org.apache.hadoop.fs.FileSystem.exists(FileSystem.java:1397)
        at shark.execution.FileSinkOperator.processPartition(FileSinkOperator.scala:105)
        .......
commit @aa5f721 resolve it in FileSinkOperator.execute. it does not work on the first qeury sql, as Hive compiler invoked before FileSinkOperator.execute. so i moved it to the start of shark client launch.