Fix several issues in recent alarms changes

The patch fixes several issues introduced in ff5e0423492a4931b188e48e2599962f1013a377:

- dcache-common imports hikaricp, which means that several components that
  don't make use of databases now pull in database related code (like the srm client).

- Missing @Override annotations in AlarmEnabledDataSource

- Redundant shutdown method in AlarmEnabledDataSource (use close)

- Infinite loop in uncaught exception handler (on IOException that isn't an
  out of file descriptor error, the code would loop forever)

- Complex code before kill on fatal JVM error (which in case of OOM may lead to
  another OOM rather than a shutdown)

To fix the HikariCP dependency I had to update to HikariCP 2.0.1.

Target: trunk
Require-notes: no
Require-book: no
Acked-by: Albert Rossi <arossi@fnal.gov>
Patch: https://rb.dcache.org/r/7188/