md-sal: sync commons-lang dependency
md-sal: sync commons-lang dependency

topology-lldp-discovery is currently specifying 2.6 commons-lang
dependency whereas the controller is dependent on 2.4.  Bring md-sal in
sync w/ the controller by dropping back to 2.4.

Change-Id: Ifb340ceef25f866cf606c4733ade80e78aea0e31
Signed-off-by: Chris Wright <e829bd48de90b6e1a1950750fa8ca2bb62f273d4@sous-sol.org>

Sushma7785/OpenDayLight-Load-Balancer,my76128/controller,tx1103mark/controller,aryantaheri/controller,tx1103mark/controller,opendaylight/controller,aryantaheri/controller,aryantaheri/controller,mandeepdhami/controller,inocybe/odl-controller,Johnson-Chou/test,mandeepdhami/controller,522986491/controller,violinlakshmi/opendaylight,tx1103mark/controller,my76128/controller,inocybe/odl-controller,aryantaheri/monitoring-controller,violinlakshmi/opendaylight,aryantaheri/monitoring-controller,violinlakshmi/opendaylight,my76128/controller,Sushma7785/OpenDayLight-Load-Balancer,aryantaheri/monitoring-controller,Johnson-Chou/test,522986491/controller,tx1103mark/controller,mandeepdhami/controller,my76128/controller,mandeepdhami/controller,aryantaheri/monitoring-controller