Branch HEAD

b=15797
i=huanghua
i=vitaly

Misc fix for updating file {a/m/c}time as following policy:
1) Lustre file "{a/m/c}time" should base on client-side clock, including all
the file operations.
2) All the client-side clocks should be synchronized. It is no matter whether
the server-side clocks are synchronized with client-side ones or not.
3) File "ctime" is increased only.
4) File "{a,m}time" are increased only, except "utime()" operation can change
them backwards.