Summary:
Fix the code in FuseChannel::processSession() to look at the errno value
instead of the return value from `read()` when checking for ENODEV.
I accidentally broke this in D7436867. This wasn't causing any major issues,
since we would still break out of the loop, but it caused us to incorrectly
print warning messages about receiving an unexpected error. We would also
print this error message once per FUSE thread rather than just once for the
mount point.
Reviewed By: bolinfest
Differential Revision: D8109889
fbshipit-source-id: 9a53ca47b436ccf6731144ee2b829131339b6445
dac67ee976