Log Message:
Update databases/apache-cassandra to 1.2.15.

Notable changes in 1.2.14
- Batchlog replay can be, and is throttled by default now.
  See batchlog_replay_throttle_in_kb setting in cassandra.yaml.

Notable changes in 1.2.11
- Added a new consistency level, LOCAL_ONE, that forces all CL.ONE operations
  to execute only in the local datacenter.
- New replace_address to supplant the (now removed) replace_token and
  replace_node workflows to replace a dead node in place.  Works like the
  old options, but takes the IP address of the node to be replaced.

Notable changes in 1.2.9
- A history of executed nodetool commands is now captured.
  It can be found in ~/.cassandra/nodetool.history. Other tools output files
  (cli and cqlsh history, .cqlshrc) are now centralized in ~/.cassandra,
  as well.
- A new sstablesplit utility allows to split large sstables offline.
- After performance testing for CASSANDRA-5727, the default LCS filesize
  has been changed from 5MB to 160MB.

Notable changes in 1.2.5
- Custom secondary index support has been added to CQL3. Refer to
  CQL3 documentation (http://cassandra.apache.org/doc/cql3/CQL.html)
  for details and examples.

Full release notes and changelogs:

https://git-wip-us.apache.org/repos/asf?p=cassandra.git;f=NEWS.txt;hb=refs/tags/cassandra-1.2.15
https://git-wip-us.apache.org/repos/asf?p=cassandra.git;f=CHANGES.txt;hb=refs/tags/cassandra-1.2.15