[HBASE-7511] Export preads latency metrics from HRegionServer metrics

Author: rshroff

Summary:
HBase already populates the preads latencies at HFile level but does not
export it via jmx. This change exports the fsPreadlatency metrics.

It also gets rid of the fsReadLatency metrics because these are not
populated as HBase now does only preads.

Test Plan:
Tested on hbase817.ash3 with custom build. After RS restart the metrics
were getting populated.

http://fburl.com/9226339 (check 3:45pm onwards)
http://fburl.com/9226350 (")

Reviewers: liyintang

Reviewed By: liyintang

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D671587

Task ID: 1996587

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1432704 13f79535-47bb-0310-9956-ffa450edef68
[Master] Print locality and dispersion for the current assignment plan in a specific format

Author: adela

Summary:
added a method which will allow printing locality and
dispersion per table in the same format like in HBaseLocalityCheck

Test Plan:
Ran RegionPlacement -ld
tested on tsh25, sample output of 1 table:
13/01/03 15:10:47 INFO master.RegionPlacement: For Table: MailBox_cell5_v1 ; #Total Regions: 1760 ; The average locality for primary is 69.59913 %
13/01/03 15:10:47 INFO master.RegionPlacement: For Table: MailBox_cell5_v1 ; #Total Regions: 1760 ; The average locality for secondary is 4.718978 %
13/01/03 15:10:47 INFO master.RegionPlacement: For Table: MailBox_cell5_v1 ; #Total Regions: 1760 ; The average locality for tertiary is 4.8160424 %
13/01/03 15:10:47 INFO master.RegionPlacement: For Table: MailBox_cell5_v1 ; #Total Regions: 1760 ; The average dispersion score is 1.0

Reviewers: liyintang

Reviewed By: liyintang

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D670270

Task ID: 1979096

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1432705 13f79535-47bb-0310-9956-ffa450edef68