Make class for managing list of vc_engine_info_s

Make class for managing list of vc_engine_info_s

- Requirement:
g_engine_list is shared memory, so thread safe access for g_engine_list
is needed.

- Contents:
This patch makes new classes for accessing list of vc_engine_info_s
instances. Through this patch, all other functions in this module can
access list of vc_engine_info_s instances in a thread safe way using new
class iinstance introduced by this patch.
This new class will protect each engine information element using mutex,
so the class will assure to prevent race condition.

Change-Id: I455a5effb5076119be220936fd26a27143e72081
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>