nfscl: Improve the console message for NFSERR_NOFILEHANDLE

Since a NFSERR_NOFILEHANDLE reply from an NFSv4 server
usually means that the file system is not exported on
the server, change the console log message to indicate
that.

(cherry picked from commit 6032cf3d6fb5d2e81ff463400bc0c6c8e00b3c3f)