Fallback to COPY for mutators when MOVE ioctl fails with EBUSY

While we can handle EBUSY by waiting for sometime and then retrying,
that's not a good idea for mutator threads. Falling back to COPY ioctl
is the most robust and timely resolution. Fortunately, this happens very
rarely, and hence not a problem.

Flag: EXEMPT bugfix
Bug: 422905336
Bug: 343220989
Test: test infra
Change-Id: Ifa506cdd3c8022b3cbb1fbb4db8438fcaa150fe9
2 files changed