LU-10822 utils: stop bogus buffer overflow errors

LU-10822 utils: stop bogus buffer overflow errors

Over-zealous Fortify checks assume that the buffer being used for
snprintf() in get_lmd_info() is sizeof(*lmd) when in fact a larger
buffer has been allocated.  This causes runtime checks to fail and
lfs to core dump:

   *** buffer overflow detected ***: /usr/bin/lfs terminated

Instead of printing directly into "struct lov_user_mds_data", use
a generic buffer to hold the filename passed into the ioctl and
the return data.

There are several places in the code which do the same operations,
namely cb_getstripe(), get_lmd_info(), and ct_md_getattr(), so
change them all to call get_lmd_info() or a new get_lmd_info_fd()
helper to consolidate common code.  Also check the return values
from snprintf() in case there are new callers of this code in the
future that do not actually pass large-enough buffers.

Test-Parameters: clientdistro=ubuntu1604 serverdistro=el7 testlist=sanity
Test-Parameters: trivial testlist=sanity-hsm
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I41b1fcba1f7937fbce3cc7180ed5d73d067cab07
Reviewed-on: https://review.whamcloud.com/31822
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>