pool: Clean up HSM storage handler

Addresses code smell in HsmStorageHandler2 class.

- Prefer setter injection over constructor injection

- Prefer annotated CLI command

- Document CLI commands

- Avoid raw types

- Avoid dead code

- Consistent source code formatting

- Prefer logging patterns over string concatenation

- Embed CLI command in HsmStorageHandler2. Having them in a separate
  class led to an overly complex interface for HsmStorageHandler2 and
  led to race conditions and inefficient code.

This is the first of several patches for HsmStorageHandler2.

Target: trunk
Require-book: no
Require-notes: no
Acked-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Patch: http://rb.dcache.org/r/5478/