Some unsolicited slsb code cleanup
- remove unnecessary/duplicate class level datasource annotations
- use DatabaseTypeFactory.getDefaultDatabseType() where appropriate
- add missing statement close in ResourceAvailabilityManagerBean
- use util safeClose methods as appropriate
[1127029] Agent [null] would like to connect to this server
The issue here is that 'rhqctl install' does not make provisions for an
existing agent on the machine.  When installing an RHQ Server or Storage
Node it is then expected that RHQ components be managed by the rhqctl
facility.  This is made possible when upgrading from pre-rhqctl versions
by the 'rhqctl upgrade' --from-server-dir and --from-agent-dir options,
which allow an upgrade to "pull in" the existing components on the machine.
The missing use case is this one, when not upgrading but rather installing.
So, this commit adds the --from-agent-dir option to 'rhqctl install'.
Allowing a formerly installed RHQ Agent to be updated (as needed) and
pulled under rhqctl, moving it to the expected location of sibling
directory to the rhq-server installation directory (and not installing
a new agent, which caused the reported issue)
- Also, fix an issue in 'rhqctl upgrade --from-agent-dir' where the new
  agent was not actually moved to the proper sibling directory.  I believe
  this affected RHQ 4.12 (and possibly JON 3.2)