bullhead_defconfig: disable NF_TARGET_REJECT_SKERR

Disable forcing socket error when rejecting with icmp* for now
due to frequent kernel crash.

Bug: 28424847
Change-Id: I3926b2b160fbafe8597d0442b297bd1accf70b4b
Signed-off-by: Thierry Strudel <tstrudel@google.com>