Disable eager-locks on NetBSD for 3.4 branch

As described in https://bugzilla.redhat.com/show_bug.cgi?id=1005526
eager-locks are broken on release-3.4, at least for NetBSD. This
change disable them by default, leaving the admin the possibility
to explicitely enable the feature if needed.

BUG: 1005526
Change-Id: I6f1b393865b103ec56ad5eb5143f59bb8672f19c
Signed-off-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-on: http://review.gluster.org/6020
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>