Do not use cat in sysctl-set-value

Use of cat | grep is an anti-pattern, grep can read files, so drop
the use of cat, saving two processes being forked off.

Change-Id: I64bf8aad5bebcd3f2f89c67ac47d8e527a5d9117
Switch from upstart to os-refresh-config for MySQL server-id's

This is both more reliable, and more cross-platform. With the
mysql element, this upstart job is never run, as a sysvinit rather
than upstart job triggers mysql.

Change-Id: I208310048d7617ec7726eceee9e4e269f1473510
Merge "Switch from upstart to os-refresh-config for MySQL server-id's"
Merge "Do not use cat in sysctl-set-value"