Enable multi-threaded nova API servers

Add an additional worker thread for each nova service: compute, ec2 and
metadata.  Any real deployment will be using multiple API server
threads, so lets make devstack test that scenario.  With this patch we
will have four worker threads for each type of API server.

Change-Id: I09f4c6f57e71982b8c7fc92645b3ebec12ff1348
Provide a means of setting vmdk custom properties via image filename

Custom properties for vmdk disk type, storage adapter type, and
networking adapter type can now be retrieved from a vmdk image's
filename. The filename format is defined as:

  <name>-<disk type>:<storage adapter>:<network adapter>

An example filename following this format would be
debian-2.6.32-i646-thin:ide:VirtualE1000. If the vmdk filename does not
match the above format then underlying nova driver will supply default
values.

Change-Id: I83483d20f984250bd8154d8e270b2e801d2df303
Closes-bug: #1221044
Missing pxelinux.0 on RedHat systems

On a RedHat system the syslinux binaries are located in a different
directory.

Change-Id: I3b7a111e82e8845b6222c57fb2cfb725d9bb1dd7
Merge "Provide a means of setting vmdk custom properties via image filename"
Merge "Missing pxelinux.0 on RedHat systems"
Merge "Enable multi-threaded nova API servers"