shell: refactor boot to use _print_server

In the shell command when we use the command boot, at the end
we use code to print some server information.
We should use the already defined function _print_server.

Change-Id: I133d7706458c71974ba464ab686cf3679a562592
Closes-Bug: #1265534
Merge "shell: refactor boot to use _print_server"