libceph: advertise support for keepalive2

We are the client, but advertise keepalive2 anyway - for consistency,
if nothing else.  In the future the server might want to know whether
its clients support keepalive2.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Yan, Zheng <zyan@redhat.com>

include/linux/ceph/ceph_features.h

@@ -107,6 +107,7 @@ static inline u64 ceph_sanitize_features(u64 features)
 	 CEPH_FEATURE_OSDMAP_ENC |		\
 	 CEPH_FEATURE_CRUSH_TUNABLES3 |		\
 	 CEPH_FEATURE_OSD_PRIMARY_AFFINITY |	\
+	 CEPH_FEATURE_MSGR_KEEPALIVE2 |		\
 	 CEPH_FEATURE_CRUSH_V4)
 
 #define CEPH_FEATURES_REQUIRED_DEFAULT   \