poolmanager: Make PSU collections thread safe and add accessors

The patch adds getters to the PSU to allow the 'bean properties' shell
commands to inspect the structure. Some entities were already exposed
through getters, others where not. Some entities were exposed through
non-getter methods.

While doing so, I discovered that many entities use non-thread safe
maps and sets internally. Even though the PSU uses a reader-writer
lock internally to protect updates, this isn't enough as we leak
references to the entities to the outside. Thus we can have concurrent
writes and reads on those collections. I replaced the collections
with thread safe equivalents.

I added setters and getters for many fields that were previously
accessed directly.

Target: trunk
Require-notes: yes
Require-book: no
Acked-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Patch: http://rb.dcache.org/r/5607/