XenServer hypervisor plugin

Convert XenServer hypervisor configuration in Nova to the new plugin setup.

Change-Id: I8916560ca3f2dae8b8d8bcb60b7aa2eb5984cbcb
XenAPI: Get the management network dynamically

xenbr0 is correct for most installations, but not all.  Notable xenserver-core
may use a differently named device.  Since we can auto detect this, remove the
config and do so.

Change-Id: I989f6ddd5ffb526ab350f263ef6fc402c596304a
Fix "instal_prereqs.sh" typo

Change-Id: I745b159aea70412d424df506af0e3d1ca2d78034
install_pip script fails if pip was not installed

'set -o errexit' recently added to the pip installer script, which causes
the script fail when it does not able to find an already installed pip.

This change handles the situation when pip is not installed.

Change-Id: I18a42d13c4be6699db21ec5b6a095a88a199912d
Merge "Fix "instal_prereqs.sh" typo"
Specify agent mode and service cluster uuid for nicira plugin

Supports blueprint nsx-integrated-services

Change-Id: Ib02716fe447f1d7f47f2f49d16f0d2ad7afe741f
Merge "install_pip script fails if pip was not installed"
Merge "XenAPI: Get the management network dynamically"
Merge "XenServer hypervisor plugin"