client: update dirfragtree/fragmap according to mds request reply

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
client: fix Client::trim_caps()

allow trimming non-auth caps if the issued auth caps include all
caps client wants/uses.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>