fs: normalize file open flags internally used by cephfs

fs: normalize file open flags internally used by cephfs

The file open flags (O_foo) are platform specific. Normalize these flags
before they are send to the MDS. For processing of client messages the
MDS should only compare to these normalized flags.
Otherwise this can lead to bogus flags getting transmitted on ppc64.

Signed-off-by: Jan Fajerski <jfajerski@suse.com>
(cherry picked from commit 88d2da5e93198e69435e288ce00d216d5fe27f80)

Conflicts:
	src/client/Client.cc - trivial resolution, add
          ceph_flags_sys2wire when flags are logged