use pgrep instead of pidof; ensure packages exist

The tests are giving failures that are unfortunately being ignored.
One of which is that pidof is not available by default on all platforms,
and on some platforms is not available at all (el7).  Same with sysctl.

There are a couple of fixes:
* run the large embedded test `shell` with `set -euo pipefail` to
trigger script errors to be handled.
* install the procps or procps-ng package which provides the tools
such as pgrep, pkill, sysctl, etc.

Signed-off-by: Rich Megginson <rmeggins@redhat.com>

tests/tasks/create_test_interfaces_with_dhcp.yml

@@ -5,12 +5,28 @@
     name: dnsmasq
     state: present
 
+- name: Install pgrep, sysctl
+  package:
+    name: procps
+    state: present
+  when:
+    - ansible_os_family == 'RedHat'
+    - ansible_distribution_major_version is version('6', '<=')
+
+- name: Install pgrep, sysctl
+  package:
+    name: procps-ng
+    state: present
+  when:
+    - ansible_os_family == 'RedHat'
+    - ansible_distribution_major_version is version('7', '>=')
 
 - name: Create test interfaces
   shell: |
+    set -euo pipefail
     ip link add {{ dhcp_interface1 }} type veth peer name {{ dhcp_interface1 }}p
     ip link add {{ dhcp_interface2 }} type veth peer name {{ dhcp_interface2 }}p
-    if [ -n "$(pidof NetworkManager)" ];then
+    if [ -n "$(pgrep NetworkManager)" ];then
       nmcli d set {{ dhcp_interface1 }} managed true
       nmcli d set {{ dhcp_interface2 }} managed true
       # NetworkManager should not manage DHCP server ports
@@ -22,7 +38,7 @@
 
     # Create the 'testbr' - providing both 10.x ipv4 and 2620:52:0 ipv6 dhcp
     ip link add name testbr type bridge forward_delay 0
-    if [ -n "$(pidof NetworkManager)" ];then
+    if [ -n "$(pgrep NetworkManager)" ];then
       # NetworkManager should not manage DHCP server ports
       nmcli d set testbr managed false
     fi