Add new flag variable for checking state

Add new flag variable for checking state

- Issue:
The engine did not call ttse_main(), but the engine library works like
that ttse_main() was already invoked.

- Solution:
The APIs provided by engine library checks g_is_terminate flag variable
for checking whether ttse_main() is invoked or not. However,
g_is_terminate variable is for checking whether ttse_terminate() is
invoked not for checking ttse_main() invocation. So even if the engine
does not call ttse_main(), the library could not know that ttse_main()
was not invoked yet. Thus, this patch adds new flag variable for
ttse_main() invocation.

Change-Id: I82e1df3abe2f685b19a6cd5a85c84c21d28d9624
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>