pinmanager,srm,spacemanager,xrootd: Fix pool monitor expiration

The pool manager state (aka pool monitor) is cached in a number of
other services. A recent change modified the cache logic to trigger
in-thread asynchronous updates rather than dedicated an entire thread
to the update. The Guava cache class is configured to trigger an update
after 20 seconds, however the update is asynchronous, meaning that the
first access after 20 seconds will still get the old data. There is a
total lifetime of 10 minutes, meaning that once the entry is 10 minutes
old, it is purged and a blocking update is done instead (i.e. you
never get data older than 10 minutes).

Unfortunately the cached pool state in pool monitor is considered
invalid after 5 minutes and the pool is then treated as offline. On
a lightly loaded system this causes some strange effects.

The immediate fix is to reduce the max lifetime to 3 minutes (allowing
some slack up to the 5 minute lifetime of the pool data). An async.
update is still triggered after 20 seconds.

Longer term, the pool information should be channelled directly from
pools to the services that need it.

Target: trunk
Request: 2.9
Require-notes: yes
Require-book: no
Acked-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Patch: https://rb.dcache.org/r/7055/
(cherry picked from commit ab39955ff726598e30f8d9ff714b96e1d9bb27ec)
Merge pull request #629 from gbehrmann/fix/2.9/rb7055

Fix/2.9/rb7055