Add a test for simultaneous device access
Add a test for simultaneous device access

Add parallel_test.py to verify simultaneous device access is handled
correctly.

wjzhang/pyOCD,matthewelse/pyOCD,pyocd/pyOCD,wjzhang/pyOCD,mesheven/pyOCD,mesheven/pyOCD,matthewelse/pyOCD,flit/pyOCD,mbedmicro/pyOCD,0xc0170/pyOCD,flit/pyOCD,mesheven/pyOCD,mbedmicro/pyOCD,pyocd/pyOCD,matthewelse/pyOCD,wjzhang/pyOCD,0xc0170/pyOCD,0xc0170/pyOCD,mbedmicro/pyOCD