Correctly handle EINTR return from futex

We should handle EINTR the same way we do EAGAIN: they're both
transient failures. Either way, higher-level code (see
ReaderWriterMutex::SharedLock) will do the right thing, loop around,
and try again.

Test: code inspection
Change-Id: I1eb7fb6851cc1a65acc9a0cf7cbeef787b6b28b6
1 file changed