Add ExecQuiet() to run a command and capture all output. Used in the CM to capture the output of varuous commands so that the logs can be sent to the user, with formatting.
Add ExecQuiet() to run a command and capture all output. Used in the
CM to capture the output of varuous commands so that the logs can be
sent to the user, with formatting.

Add subgroup handing in FlipToGeniUser(), and also add ResetGroups()
to change the user's group membership, since the slice experiments are
now created in a subgroup of GeniSlices (named by the user's SA).

nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome