Fix sonar issues in integrity monitor

Fix sonar issues in integrity monitor

Used Eclipse Refactor->Extract Method to reduce cyclomatic
complexity.
Flattened nested FpManager class into IntegrityMonitor class.
Changed some strings to StringBuilder, where lots of concatenation
was being done.
Simplified some things by eliminating some try/catch blocks where
an exception can't actually (except may an out-of-memory exception).
Also addressed some sonar issues in the tests (e.g., use "<>" where
appropriate).
Eliminated some assertException methods, replacing them with assertj
methods.
Did not attempt to increase junit coverage.

Change-Id: I311acaffcd87f0cbbf382c06c7fa26177007abd5
Issue-ID: POLICY-1791
Signed-off-by: Jim Hahn <jrh3@att.com>