PolicyKeyFeature: avoid complex global constants

PolicyKeyFeature: avoid complex global constants

PolicyKeyFeature is used by other global instances in cynara-test
and cannot assume that the initialization of its own static constants
happens first, unless it enforces initialization by embedding
these constants in method calls.

Upstream-status: Submitted [https://github.com/Samsung/cynara/issues/9]
Change-Id: Ifa6dcd44ce059cf3ec8c99764bd6ea0c677cdd6d
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Radoslaw Bartosiak <r.bartosiak@samsung.com>