Silence a use-after-free warning from the analyzer

The analyzer is known to be very conservative in the face of atomic
operations (e.g. https://bugs.llvm.org/show_bug.cgi?id=34365); this case
is no different.

It's concerned that `delete this;` might read a different value for
`flags`, and proceed to delete `refs`. Since there are many comments
explaining why this won't happen (and it all looks sane to me), use a
NOLINT to silence this warning.

Analyzer warning:
system/core/libutils/RefBase.cpp:445:5: warning: Use of memory after it
is freed

Bug: 27101951
Test: mma. Use-after-free warning is gone.
Change-Id: Ic1623971bd1bad546fbb12a79439116c89a6762d