[CIFS] reopen file via newer posix open protocol operation if available

If the network connection crashes, and we have to reopen files, preferentially
use the newer cifs posix open protocol operation if the server supports it.

Signed-off-by: Steve French <sfrench@us.ibm.com>

diff --cc fs/cifs/cifsproto.h
Simple merge

diff --cc fs/cifs/dir.c
Simple merge

diff --cc fs/cifs/file.c
Simple merge