Support generic Hadoop Compatible Filesystem (short version)

This is a short version of #388.
@dcapwell here is the error. The cause of the error is that `mapred.system.dir` cannot be found in `Configuration`, while it is set in here https://github.com/amplab/tachyon/pull/437/files#diff-37224ab9cb80b91d69d9c708ea509debR28


Running tachyon.util.UnderfsUtilsTest
Tests run: 2, Failures: 0, Errors: 2, Skipped: 0, Time elapsed: 0.354 sec <<< FAILURE!
loadUnderFsTest(tachyon.util.UnderfsUtilsTest)  Time elapsed: 0.354 sec  <<< ERROR!
java.lang.RuntimeException: java.lang.NullPointerException
	at org.apache.hadoop.fs.glusterfs.GlusterVolume.sameVolume(GlusterVolume.java:98)
	at org.apache.hadoop.fs.glusterfs.GlusterVolume.setConf(GlusterVolume.java:138)
	at org.apache.hadoop.fs.RawLocalFileSystem.initialize(RawLocalFileSystem.java:92)
	at org.apache.hadoop.fs.glusterfs.GlusterVolume.initialize(GlusterVolume.java:80)
	at org.apache.hadoop.fs.FilterFileSystem.initialize(FilterFileSystem.java:86)
	at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:2316)
	at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:90)
	at org.apache.hadoop.fs.FileSystem$Cache.getInternal(FileSystem.java:2350)
	at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2332)
	at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:369)
	at org.apache.hadoop.fs.Path.getFileSystem(Path.java:296)
	at tachyon.UnderFileSystemHdfs.<init>(UnderFileSystemHdfs.java:71)
	at tachyon.UnderFileSystemHdfs.getClient(UnderFileSystemHdfs.java:44)
	at tachyon.UnderFileSystem.get(UnderFileSystem.java:51)
	at tachyon.UnderFileSystem.get(UnderFileSystem.java:39)
	at tachyon.UnderFileSystemsUtils.mkdirIfNotExists(UnderFileSystemsUtils.java:30)
	at tachyon.master.LocalTachyonMaster.<init>(LocalTachyonMaster.java:73)
	at tachyon.master.LocalTachyonMaster.create(LocalTachyonMaster.java:135)
	at tachyon.master.LocalTachyonCluster.start(LocalTachyonCluster.java:158)
	at tachyon.util.UnderfsUtilsTest.before(UnderfsUtilsTest.java:42)