ASACORE-1058: Fix qcc::String assign that wanted to append instead.

Trying to be clever when the refCount of the context is 1, qcc::String
assign() incorrectly appended the new string instead of replacing.

Change-Id: Id4236e4bc4fda6feb3ed5a83675b0114ecdbbe50
Signed-off-by: Todd Malsbary <tmalsbar@qce.qualcomm.com>
Merge "ASACORE-1058: Fix qcc::String assign that wanted to append instead."