Qemu test case: wait dynamically until booted

Created by: ollieparanoid

Introduction

We have a test case, that performs full installations with with XFCE4 and Plasma Mobile. After each installation is through, we run pmbootstrap qemu and connect to the VM via SSH to check for specific running processes.

Change

Before this commit, we assumed that the boot takes 90 seconds at most and then the processes should exist. But sometimes the boot is faster (so Travis waits just doing nothing) and sometimes it is slower (which causes the test case to fail), all depending on the current workload of the Travis CI servers. Now we try to find the processes we're interested in each second for 3 minutes until we either succeed or reach the time limit.