Ubuntu trusty containers need 4.15 kernel to avoid performance hit

[nuclearsandwich]

This issue presents a solution for the issue reported in ros-infrastructure/ros_buildfarm#535.

Summary: Spectre and Meltdown mitigations in the Ubuntu 16.04 kernel have started causing a significant performance impact when running apt-get in Ubuntu 14.04 containers. Host systems on the 14.04 kernel, 18.04 kernel, and the 16.04 HWE edge kernel (4.15-based) all function as before.

Conclusion: build.ros.org is going to migrate its build agent hosts to the hardware enablement edge kernel. It's less work and less disruptive than migrating the buildfarm_deployment to bionic.

If you're setting up a buildfarm and are not configuring packages to build on Ubuntu Trusty (ROS Indigo) then this recommendation does not necessarily apply.

[nuclearsandwich]

Dropping a breadcrumb for future investigation
Kernel update related failure in http://build.ros.org/job/Ibin_uT64__realsense_camera__ubuntu_trusty_amd64__binary/49/

07:50:39 libkmod: ERROR ../libkmod/libkmod.c:556 kmod_search_moddep: could not open moddep file '/lib/modules/4.15.0-20-generic/modules.dep.bin'
07:50:39 modinfo: ERROR: Module alias uvcvideo not found.