neutron-legacy: Update after DEFAULT.root_helper removal

Update after change I17cd62c8763430bf3a4b67ab5e9cf5b736065133 .

Closes-Bug: #1483501
Change-Id: Ieb5270484205cffe4ec97db0d59f012d1e7708d4
diff --git a/lib/neutron-legacy b/lib/neutron-legacy
index 6412609..7dddde1 100644
--- a/lib/neutron-legacy
+++ b/lib/neutron-legacy
@@ -977,7 +977,7 @@
     iniset $Q_DHCP_CONF_FILE DEFAULT verbose True
     iniset $Q_DHCP_CONF_FILE DEFAULT debug $ENABLE_DEBUG_LOG_LEVEL
     iniset $Q_DHCP_CONF_FILE DEFAULT use_namespaces $Q_USE_NAMESPACE
-    iniset $Q_DHCP_CONF_FILE DEFAULT root_helper "$Q_RR_COMMAND"
+    iniset $Q_DHCP_CONF_FILE agent root_helper "$Q_RR_COMMAND"
     if [[ "$Q_USE_ROOTWRAP_DAEMON" == "True" ]]; then
         iniset $Q_DHCP_CONF_FILE agent root_helper_daemon "$Q_RR_DAEMON_COMMAND"
     fi
@@ -1012,7 +1012,7 @@
     iniset $Q_L3_CONF_FILE DEFAULT verbose True
     iniset $Q_L3_CONF_FILE DEFAULT debug $ENABLE_DEBUG_LOG_LEVEL
     iniset $Q_L3_CONF_FILE DEFAULT use_namespaces $Q_USE_NAMESPACE
-    iniset $Q_L3_CONF_FILE DEFAULT root_helper "$Q_RR_COMMAND"
+    iniset $Q_L3_CONF_FILE agent root_helper "$Q_RR_COMMAND"
     if [[ "$Q_USE_ROOTWRAP_DAEMON" == "True" ]]; then
         iniset $Q_L3_CONF_FILE agent root_helper_daemon "$Q_RR_DAEMON_COMMAND"
     fi
@@ -1036,7 +1036,7 @@
     iniset $Q_META_CONF_FILE DEFAULT verbose True
     iniset $Q_META_CONF_FILE DEFAULT debug $ENABLE_DEBUG_LOG_LEVEL
     iniset $Q_META_CONF_FILE DEFAULT nova_metadata_ip $Q_META_DATA_IP
-    iniset $Q_META_CONF_FILE DEFAULT root_helper "$Q_RR_COMMAND"
+    iniset $Q_META_CONF_FILE agent root_helper "$Q_RR_COMMAND"
     if [[ "$Q_USE_ROOTWRAP_DAEMON" == "True" ]]; then
         iniset $Q_META_CONF_FILE agent root_helper_daemon "$Q_RR_DAEMON_COMMAND"
     fi