rhel: user/group openvswitch does not exist

Default ownership[1] for config files is failing on an empty system:
  Running scriptlet: openvswitch-2.9.0-3.fc28.x86_64
warning: user openvswitch does not exist - using root
warning: group openvswitch does not exist - using root
...

Required user/group need to be created in %pre as documented in
Fedora guideline[2]

[1] 951d79e

[2] https://fedoraproject.org/wiki/Packaging:UsersAndGroups#Dynamic_allocation

Submitted-at: #223
Signed-off-by: Alan Pevec <alan.pevec@redhat.com>
Co-authored-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Aaron Conole <aconole@redhat.com>
Acked-by: Markos Chandras <mchandras@suse.de>
Signed-off-by: Russell Bryant <russell@ovn.org>

rhel/openvswitch-fedora.spec.in

@@ -92,8 +92,7 @@ Requires: openssl hostname iproute module-init-tools
 #Upstream kernel commit 4f647e0a3c37b8d5086214128614a136064110c3
 #Requires: kernel >= 3.15.0-0
 
-Requires(post): /usr/bin/getent
-Requires(post): /usr/sbin/useradd
+Requires(pre): shadow-utils
 Requires(post): /usr/bin/sed
 %if %{with dpdk}
 Requires(post): /usr/sbin/usermod
@@ -386,17 +385,23 @@ rm -rf $RPM_BUILD_ROOT
     fi
 %endif
 
+%pre
+getent group openvswitch >/dev/null || groupadd -r openvswitch
+getent passwd openvswitch >/dev/null || \
+    useradd -r -g openvswitch -d / -s /sbin/nologin \
+    -c "Open vSwitch Daemons" openvswitch
+
+%if %{with dpdk}
+    getent group hugetlbfs >/dev/null || groupadd hugetlbfs
+    usermod -a -G hugetlbfs openvswitch
+%endif
+exit 0
+
 %post
 if [ $1 -eq 1 ]; then
-    getent passwd openvswitch >/dev/null || \
-        useradd -r -d / -s /sbin/nologin -c "Open vSwitch Daemons" openvswitch
-
     sed -i 's:^#OVS_USER_ID=:OVS_USER_ID=:' /etc/sysconfig/openvswitch
 
 %if %{with dpdk}
-    getent group hugetlbfs >/dev/null || \
-        groupadd hugetlbfs
-    usermod -a -G hugetlbfs openvswitch
     sed -i \
         's@OVS_USER_ID="openvswitch:openvswitch"@OVS_USER_ID="openvswitch:hugetlbfs"@'\
         /etc/sysconfig/openvswitch