[dhcp_relay] fix the compile error introduced by the fixed issue of '#3316', change the sample_output file of 'wait_for_intf.sh'#3325

jleveque merged 3 commits intosonic-net:mastersonic-net/sonic-buildimage:masterfrom

wangshengjun:dhcp_relay_bugwangshengjun/sonic-buildimage:dhcp_relay_bugCopy head branch name to clipboard