tizen: Use OS enrollee

To support fedora-24 for ARTIK7

Change-Id: I8d40700b8f19fcbc71cb3ad3235cda990290792d
Origin: https://gerrit.iotivity.org/gerrit/#/c/23299/Signed-off-by: Philippe Coval <philippe.coval@osg.samsung.com>
(cherry picked from commit 56ce7b64)

tools/tizen/iotivity.spec

@@ -73,7 +73,7 @@ BuildRequires: python-accel-aarch64-cross-aarch64
 %endif
 
 # Default values to be eventually overiden BEFORE or as gbs params:
-%{!?ES_TARGET_ENROLLEE: %define ES_TARGET_ENROLLEE tizen}
+%{!?ES_TARGET_ENROLLEE: %define ES_TARGET_ENROLLEE %{TARGET_OS}}
 %{!?LOGGING: %define LOGGING 1}
 %{!?RD_MODE: %define RD_MODE CLIENT}
 %{!?RELEASE: %define RELEASE 1}