Add script for connecting static jenkins slaves

Add script for connecting static jenkins slaves

Script from [1] adapted for akraino, both for production and for
sandbox. It configures monit and connects the slave to the LF master

Usage for production:
sudo akraino/repos/ci-management/utils/jenkins-jnlp-connect.sh \
-j /home/jenkins -u jenkins -n <slave_name> -s <secret>

Usage for sandbox:
sudo akraino/repos/ci-management/utils/jenkins-jnlp-connect.sh \
-j /home/jenkins -u jenkins -n <slave_name> -s <secret> -b

[1] https://github.com/opnfv/releng/blob/master/utils/jenkins-jnlp-connect.sh

Change-Id: I7289a06a13deb3626a4c37147d6fb8b5fdd0e5ff
Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>