LU-4954 mdd: validate names before create, link, and rename

LU-4954 mdd: validate names before create, link, and rename

In lu_name_is_valid() check that the length of the ln_name is equal to
ln_namelen and check that there are no embedded slashes. Add
mdd_name_check() which calls lu_name_is_valid() and check against the
mdd ENAMETOOLONG limit. Call mdd_name_check() from
mdd_create_sanity_check(), mdd_link_sanity_check() and mdd_rename().

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I66413b796177f042fc9bd87e98338de9e5125cae
Reviewed-on: http://review.whamcloud.com/10111
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>