Ignore HTTP Whiteboard Filters

Ignore HTTP Whiteboard Filters

CustomFilterAdapterConfigurationImpl is listening for all servlet
filters being published to OSGi registry. This unfortunately means
it picks up also filters destined for HTTP Whiteboard -- such as
CustomFilterAdapter, which in turn uses ConfigurationImpl to get
its list of filters -- leading to the filter referencing itself.

Exclude Filters properly marked for HTTP Whiteboard from contributing to
the list and drop a FIXME for a future enhancement.

JIRA: AAA-235
Change-Id: I80c1264889b42a105a62cd5da4238a54554839dd
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>