extapi: switch sensitive scalar with flags mask, add non printable

there is a case of loops within the map especially when global context
and the context points to each other.

add a flag to skip dump of keys.

Change-Id: I9f9204d2b44af052196b0be0c4ad4ef3727c0768
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>