[OpenMP] Make isDone lightweight without calling synchronize

~TaskAsyncInfoWrapperTy() calls isDone. With synchronize inside isDone, we need to handle the error return from synchronize in the destructor.
The consumers of TaskAsyncInfoWrapperTy, targetDataMapper and targetKernel, both call AsyncInfo.synchronize() before exiting.
For this reason in ~TaskAsyncInfoWrapperTy(), calling synchronize() via isDone() is redundant.
This patch removes synchronize() call inside isDone() and makes it a lightweight check.
__tgt_target_nowait_query needs to call synchronize() before checking isDone().

Differential Revision: https://reviews.llvm.org/D144315