TT#76757 ec2/bootstrap.sh: wait for dpkg lock to be free
TT#76757 ec2/bootstrap.sh: wait for dpkg lock to be free

We are having problems on this stage due to dpkg is being executed
in parallel so let's try to wait until we can use it

Change-Id: Ie84f53232e0094447edd40a360ee4ae9700c3e07

sipwise/kamailio-deb-jenkins,sipwise/kamailio-deb-jenkins