mnexec: mount sysfs in each container

The sysfs filesystem is [tagged][1] with a set of namespaces when mounted, taken
from the mounting process. Among other things, this controls which network
devices will show up in /sys/class/net and /sys/class/net/bonding_masters.

Without this change, mininet will not mount sysfs in a node. Attempting to
configure a bond interface in a node will only affect the parent namespace.

This change mounts a new sysfs filesystem in each node. To prevent this mount
from affecting the parent namespace the mount namespace is also unshared.

[1]: https://www.kernel.org/doc/Documentation/filesystems/sysfs-tagging.txt
Do not resolve addresses
Uploading MiniEdit 2.1.0.7.1

Many changes since master version.
- save/load topologies
- host, controller, switch and link properties
- link actions to set status up/down
Update to 2.1.0.8
    Change the installation to a separate option as recommended with -V.
    This argument expect a parameter which is the version number of OVS you wish to install.
    install.sh -V 2.0.0

    What is nice that I tested, is that you can keep running the above to change
    which OVS version you want to test with.  Also, if a new version of OVS
    is released, just run the above again specifying the new version number.

    The version number must match the version number in the tarball file name
    like openvswitch-2.0.0.tar.gz.  In this case, the version specified
    must be 2.0.0.
Fix IVS build
assertTrue( a > b ) -> assertGreater( a, b ) for better messages
Enable batch shutdown for OVS.
Use a single ovs-vsctl command for speed/atomicity
Update to 2.1.0.8.1.  Include a fix to work around Mininet version number
checking with non-numeric characters.
Don't look through all interfaces if you don't need to.
Merge pull request #246 from rlane/newns

(pending) mnexec: mount sysfs in each container
persistent command history

Saves readline history to ~/.mininet_history.
build=False is unnecessary if topo=None, which is the default
IVSSwitch: wait for ivs to terminate before tearing down node

This was a problem when running IVS in a container. IVS would begin the process
of closing controller connections on receiving SIGTERM, but often mininet would
have continued on and removed the control network interface from the container
before it could send the FIN. The controller wouldn't know the connection had
been closed until it timed out much later.
Merge pull request #288 from rlane/history

persistent command history
Merge pull request #289 from rlane/ivs-wait

IVSSwitch: wait for ivs to terminate before tearing down node
Merge pull request #283 from ggee/ovs2install

    OVS install Ubuntu packages
Merge pull request #257 from ggee/miniedit21071

 Uploading MiniEdit 2.1.0.7.1
Ping: packet loss should be a float