Fix payload value query for external semaphores

[ahesham-arm]

When creating a CL semaphore object from a Vulkan semaphore one, we explicitly pass -1 as the file descriptor value in the case of VULKAN_EXTERNAL_SEMAPHORE_HANDLE_TYPE_SYNC_FD. According to the CL specification:

The special value -1 for fd is treated like a valid sync file
descriptor referring to an object that has already signaled. The
import operation will succeed and the semaphore will have a
temporarily imported payload as if a valid file descriptor had
been provided.

The test currently checks that the semaphore payload is unsignalled, unconditionally, which is incorrect.

Changed the test to check for the correct expected payload value.

[bashbaug]

Would it be better to get a valid SYNC_FD file descriptor for this test case instead of using the special -1 file descriptor value?

All of the other handle types seem to be getting a valid handle:

handle = semaphore.getHandle(externalSemaphoreHandleType);

[ahesham-arm]

Would it be better to get a valid SYNC_FD file descriptor for this test case instead of using the special -1 file descriptor value?

All of the other handle types seem to be getting a valid handle:

handle = semaphore.getHandle(externalSemaphoreHandleType);

I agree that we need an additional test here, because we should be covering two cases:

• Creating a semaphore with a sync fd set to -1, and checking that the payload is signalled (which is what this PR fixes)
• Creating a semaphore with a valid sync fd value other than -1, and checking that the payload is unsignalled (which I can address) in a follow up PR.