Use package-installs for undercloud elements

Ideally all elements would be using package-installs so we only
call yum once per stage, but since a lot of these elements are no
longer used this change focuses on just the elements doing one-off
package installs that I found in the undercloud install logs.

A follow-up change would be to do the same kind of audit for the
overcloud image build and fix up all of those elements.

Change-Id: Ie204c5d0aa0f48d3d93d834b51a644d8562cd2fd

elements/ironic-conductor/install.d/68-ironic-conductor-common

@@ -1,6 +0,0 @@
-#!/bin/bash
-set -eux
-set -o pipefail
-
-# ensure we have tftp and pxe requirements
-install-packages syslinux tftpd-hpa xinetd parted psmisc

elements/ironic-conductor/package-installs

@@ -0,0 +1,5 @@
+syslinux:
+tftpd-hpa:
+xinetd:
+parted:
+psmisc:

elements/openvswitch/element-deps

@@ -1 +1,2 @@
 os-svc-install
+package-installs

elements/openvswitch/install.d/74-openvswitch

@@ -1,8 +1,6 @@
 #!/bin/bash
 set -eux
 
-install-packages -m openvswitch openvswitch-switch_package
-
 if [ "$DIB_INIT_SYSTEM" == "systemd" ] ; then
     os-svc-enable -n openvswitch-switch
 fi

elements/openvswitch/package-installs

@@ -0,0 +1 @@
+openvswitch-switch_package: