polycubed crashes when SIGINT is received on boot

[mauriciovasquezbernal]

A SIGINT makes polycubed to crash with a segmentation fault when it is starting.

Example:

[2019-01-22 20:25:09.781] [polycubed] [info] loading configuration from /etc/polycube/polycubed.conf
[2019-01-22 20:25:09.783] [polycubed] [info] configuration parameters: 
[2019-01-22 20:25:09.783] [polycubed] [info]  loglevel: debug
[2019-01-22 20:25:09.783] [polycubed] [info]  daemon: false
[2019-01-22 20:25:09.783] [polycubed] [info]  pidfile: /var/run/polycube.pid
[2019-01-22 20:25:09.783] [polycubed] [info]  port: 9000
[2019-01-22 20:25:09.783] [polycubed] [info]  addr: localhost
[2019-01-22 20:25:09.783] [polycubed] [info]  logfile: /var/log/polycube/polycubed.log
[2019-01-22 20:25:09.783] [polycubed] [info] polycubed starting...
[2019-01-22 20:25:09.783] [polycubed] [info] version -128-NOTFOUND+ [git: (branch/commit): transparent_services_new/6fab8309]
^C[2019-01-22 20:25:10.595] [polycubed] [info] Caught signal 2
Segmentation fault