Tserver gets stuck if context classloader fails on first try

accumulo 2.1.x:

If a context cannot be loaded when creating the compaction dispatcher (e.g. vfs class loader failed to retrieve jars from hdfs), then it will never be reattempted and you continuously get the message at CompactableImpl:1487 (Failed to dispatch compaction...). The only way to recover is to bounce the tserver. Potentially changing the context on the table may relieve the issue but I have not tested that.

Start at CompactableImpl:1487 and trace context loading while creating the compaction dispatcher. Reproduce a failed context or class-loader retrieval, then determine the retry or recovery behavior needed so the tserver no longer requires a bounce; add coverage for the failure and recovery path.

Written by the indexing model from the issue text.