mds: do files recovery after processing cap flushes

mds: do files recovery after processing cap flushes

File recovery may update inode and trigger inode COW. MDS relies on
client caps to setup CInode::client_need_snapflush. But for a given
client, the reconnected caps may not include the flushing caps.
(Before MDS failover, client released and flushed some caps at the
same time. When MDS recovers, client re-send the cap flush and send
cap reconnect to the MDS.) This may cause later snapflush to get
dropped.

Signed-off-by: Yan, Zheng <zyan@redhat.com>