core: DbUserCacheManager: add missing modifiers

Added static and final modifiers where appropriate to utilize Java's
memory handling optimizations.

Change-Id: Ic4d6d7a2ed75584e326609ae820e054b302748a0
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: DhUserCacheManager: Remove empty else block

Change-Id: I011ca459f98494967495ae0cb8e381d7a3443c28
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: DbUserCacheManager: Remove FQDN

Remove FQDNs and replaced with imports, for better readability.

Change-Id: I8957ad7fa0317b84fd82bdd891d9dd984d9ebc26
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: DbUserCacheManager: Fix comment format

Stop using javadoc format for in-method comments.

Change-Id: Ic08e9864d2fe0129b32d882dbf997c24d9ec2c04
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: DbUserCacheManager: iterate entrySet()

Iterate over entrySet() instead of iterating over keySet() and calling
get, for better performance.

Change-Id: I8db1dd978760eb961a7e17c36a99ff4f8a2c4917
Signed-off-by: Allon Mureinik <amureini@redhat.com>