Avoid duplicated call of legacy_camera_create/destroy

Avoid duplicated call of legacy_camera_create/destroy

When user calls camera_get_device_state or camera_get_flash_state,
legacy_camera_create and legacy_camera_destroy are always called internally.
But, it's enough to call only once after muse-server starts, so update the code to avoid unnecessary call.

[Version] 0.2.68
[Profile] Common
[Issue Type] Update
[Dependency module] N/A
[Test] [M(T) - Boot=(OK), sdb=(OK), Home=(OK), Touch=(OK), Version=tizen-3.0-mobile_20170131.2]

Change-Id: I93685e0bef44b792c5c899cd0d0009012e7290cd
Signed-off-by: Jeongmo Yang <jm80.yang@samsung.com>