The framework/ssh.go code was heavily used throughout the framework
and could be useful elsewhere but reusing those methods requires
importing all of the framework.
Extracting these methods to their own package for reuse.
Only a few methods had to be copied into this package from the
rest of the framework to avoid an import cycle.
On Ubuntu (and, presumably, other distros too), the default
configuration prohibits some sysrq operations. Before performing sysrq
operations in the e2e testing, ensure that all operations are permitted.
The ifupdown commands (ifup and ifdown) are not useful on many modern
distributions. Instead, the "ip link set" set of commands are standard
linux utilities and should be available everywhere (see
http://baturin.org/docs/iproute2/).
ipupdown utilities have the added quirk that they return 0 on failure,
which makes the changed line fail silently in case ifdown didn't bring
the network down.
After the interface was brought back up, renew DHCP requests to ensure
the network is actually useable.
Signed-off-by: Chris Glass <chris.glass@canonical.com>