dm thin: fail messages with EOPNOTSUPP when pool cannot handle messages
dm thin: fail messages with EOPNOTSUPP when pool cannot handle messages

Use EOPNOTSUPP, rather than EINVAL, error code when user attempts to
send the pool a message.  Otherwise usespace is led to believe the
message failed due to invalid argument.

Reported-by: Zdenek Kabelac <fa485f84d4deb8882534f4b042b84983a8dcdd80@redhat.com>
Signed-off-by: Mike Snitzer <85e533f2e78486213c4d69f71462342ec0c62734@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs