Add namespace filtering to SSL endpoints check

Add namespace filtering to SSL endpoints check

Utility "sslendpoints" now supports scanning only selected Kubernetes
cluster namespace. To do so, add "-namespace" flag with namespace of
your choice as its argument to the executed command.

Default behavior remained unchanged, i.e. scan covers all namespaces.

Issue-ID: INT-1582
Change-Id: If5534b76bca94248a5003d735c25328648e478a1
Signed-off-by: Pawel Wieczorek <p.wieczorek2@samsung.com>
(cherry picked from commit 1a5a1ad36edcb3d8e6d041aa9ea1f622206c37f5)