This adds APIs to trigger create, delete, interface up and interface
down commands on bridge interface.
It uses following IOCTLs for sending command to linux kernel:
Add bridge iface: SIOCBRADDBR
Remove bridge iface: SIOCBRDELBR
Mark iface up/down: SIOCGIFFLAGS
CRs-Fixed: 2080924
Change-Id: I3d34dc16e9ca82dc4b550cbc83fa4120c80ad54c