BK client error messages needs to be more descriptive

[pasha-kuznetsov]

BK Client prints error messages as follows:

20171212011311.000426 [ERROR] [clientWorker-orderedsafeexecutor-0-0] [LedgerHandle.java:1055] - 
Closing ledger 4099501146997097674 due to error -101

it'd be more user-friendly if it gave a description of what -101 meant, for example:

20171212011311.000426 [ERROR] [clientWorker-orderedsafeexecutor-0-0] [LedgerHandle.java:1055] - 
Closing ledger 4099501146997097674 due to error -101:
Ledger has been fenced off. Some other client must have opened it to read

[merlimat]

👍 Nice suggestion. Also it doesn't make sense to print -101. We should rather use the enum name for that error.