TT#47856 ngcp-initial-configuration: use DHCP by default

Instead of hardcoding the IP address for the network interface
that was present at the time of invocation of ngcp-initial-configuration
let's use DHCP instead. This should prevent the system from assigning
and using an IP address that is no longer present, once it was changed
from within the AWS EC2 instance.

Change-Id: I298a2ac1a08f57e45de51c46c02d8832d2db740a

ec2-create-ce

@@ -392,7 +392,9 @@ esac
 
 if "${init_configuration}" ; then
   cat >> "${USER_DATA_FILE}" << EOF
-sed_regexp='s/^(export FORCE)=.+$/\1=yes/'
+sed_regexp=''
+sed_regexp+='s/^(export FORCE)=.+$/\1=yes/;'
+sed_regexp+='s/^(export DHCP)=.+$/\1=true/;'
 sed -ri "\${sed_regexp}" /etc/ngcp-installer/config_deploy.inc
 ngcp-installer && ngcp-initial-configuration
 EOF