mem: detach memsegs on cleanup

mem: detach memsegs on cleanup

Currently, we don't detach the shared memory on EAL cleanup, which
leaves the page table descriptors still holding on to the file
descriptors as well as memory space occupied by them. Fix it by adding
another detach stage that closes the internal memory allocator resource
references, detaches shared fbarrays and unmaps the shared mem config.

Bugzilla ID: 380
Bugzilla ID: 381

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>