Merge "Trivial strxfrm coverage improvement." am: 6900a09fe7 am: 1caae5f7f5 am: b0cef76f70 am: 661352235d

Original change: https://android-review.googlesource.com/c/platform/bionic/+/1393618

Change-Id: Iab8e8d033a566fb36c73c0620af7a903d92f5bc4