openr2(1/6): bugfix in configuration saving

Details:
  - The memcpy() call copied part of "dahdi_conf" and not "dahdi_conf.mfcr2"
  - As a result, the memcmp() in dahdi_r2_get_link() always fails
  - This cause dahdi_r2_get_link() to create new link for every channel
    (instead of a new link for every ~30 channels)
  - With the fix, far less links are generated -- so we use far less threads

Change-Id: I7259dd6272f5e46e8a6c7f5bf3e8c2ec01b8c132
Signed-off-by: Oron Peled <oron.peled@xorcom.com>