JobSplitWriter prints unnecessary warnings if EC(RS10,4) is used

Currently, JobSplitWriter compares the number of hosts for a certain block against a static value that comes from mapreduce.job.max.split.locations. The default value of this property is 10.

However, an EC schema like RS-10-4 requires at least 14 hosts. In this case, 14 block locations will be returned and JobSplitWriter prints a warning, which can confuse users.

A possible solution could check whether EC is enabled for a block and increase this value dynamically if needed. A simpler one is to simply increase the default value to a sensible number like 15.