LU-3289 gss: don't build SSK if libssl-1.0+ not available

LU-3289 gss: don't build SSK if libssl-1.0+ not available

The SSK functionality depends on libssl 1.0 or newer to have the
proper HMAC support.  If that is not available (e.g. SLES11) then
don't try to build this feature at all.

Rename the configure check to be OPENSSL_SSK since this is used in
several places, and is more clear than HAVE_INT_OPENSSL_HMAC_FUNCS.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I3b15f819bba421539664e629a4017599e23ebbe5
Reviewed-on: http://review.whamcloud.com/22806
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Minh Diep <minh.diep@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>