base-files: set kernel.core_pattern in sysctl.conf

Move the pattern setting from netifd's service script to
/etc/sysctl.conf.  Put the timestamp component '%t' just after
executable name '%e' for more natural order from output of ls command.

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

SVN-Revision: 46867

package/base-files/files/etc/sysctl.conf

@@ -1,4 +1,6 @@
 kernel.panic=3
+kernel.core.pattern=/tmp/%e.%t.%p.%s.core
+
 net.ipv4.conf.default.arp_ignore=1
 net.ipv4.conf.all.arp_ignore=1
 net.ipv4.ip_forward=1