Install nodejs for RHEL/Fedora

nodejs is required for Horizon (ships a copy of lessc internally).  I
couldn't find nodejs in the rpm list, despite it being installed in
lib/horizon.  This adds to the rpm list as NOPRIME and retains the old
install point.

RHEL6 has nodejs in EPEL now, so we remove the old hack that installed
an upstream version and add it to the install mentioned previously

Change-Id: Ib3ee2f7d77e22666c9055c8528288c01b46a95d3
xenapi: kernel_cmdline moved out from template

The kernel's cmdline was set during the initial devstack machine
installation. Thus, during second runs, the kernel's cmdline was not
updated. This patch extracts append_kernel_cmdline, and configures
domU's kernel cmdline every time. As some networking parameters are
passed through the kernel cmdline, this patch makes it possible to
change the network configuration, even if a cached devstack exists.

Related to blueprint xenapi-devstack-cleanup

Change-Id: I3b7175f4e83326c3e28825ac50625f6bd2a9a029
Merge "Install nodejs for RHEL/Fedora"
Merge "xenapi: kernel_cmdline moved out from template"