HealthMonitor sonar issues

Remove this unused "numIntervalsClusterNotHealthy" local variable.
Use "Long.parseLong" for this string-to-long conversion.
Make the enclosing method "static" or remove this set.
Change this instance-reference to a static reference.
Remove the literal "false" boolean value.
This block of commented-out lines of code should be removed.
Add the "@Override" annotation above this method signature

Issue-ID: PORTAL-647
Change-Id: I1880177f0906e6267807bbb9c0b7a81651e3c020
Signed-off-by: Dominik Mizyn <d.mizyn@samsung.com>