libdlog: isolate limiter creation

libdlog: isolate limiter creation

Limiter no longer checks whether it is enabled on construction,
it is now the caller's responsibility. This allows to construct
limiter with a limited config (for example containing just the
ruleset) and possibly to add extra rules between deciding to use
the limiter and actually creating it (so that the extras needn't
be loaded if opting out of the feature).

Change-Id: I8e6a4ad06c782f17e47cd5e90a73a150cf327eb3
Signed-off-by: Michal Bloch <m.bloch@samsung.com>