Suppress output in %pre scriptlet when adjusting users/groups

This approach is also used in other packages, e.g., systemd.
Resolves: rhbz#1876729

clevis.spec

@@ -1,6 +1,6 @@
 Name:           clevis
 Version:        14
-Release:        4%{?dist}
+Release:        5%{?dist}
 Summary:        Automated decryption framework
 
 License:        GPLv3+
@@ -118,13 +118,13 @@ desktop-file-validate \
 %meson_test
 
 %pre
-getent group %{name} >/dev/null || groupadd -r %{name}
+getent group %{name} >/dev/null || groupadd -r %{name} &>/dev/null
 getent passwd %{name} >/dev/null || \
     useradd -r -g %{name} -d %{_localstatedir}/cache/%{name} -s /sbin/nologin \
-    -c "Clevis Decryption Framework unprivileged user" %{name}
+    -c "Clevis Decryption Framework unprivileged user" %{name} &>/dev/null
 # Add clevis user to tss group.
 if getent group tss >/dev/null && ! groups %{name} | grep -q "\btss\b"; then
-    usermod -a -G tss %{name}
+    usermod -a -G tss %{name} &>/dev/null
 fi
 exit 0
 
@@ -184,6 +184,10 @@ exit 0
 %attr(4755, root, root) %{_libexecdir}/%{name}-luks-udisks2
 
 %changelog
+* Tue Sep 08 2020 Sergio Correia <scorreia@redhat.com> - 14-5
+- Suppress output in pre scriptlet when adjusting users/groups
+  Resolves: rhbz#1876729
+
 * Tue Sep 08 2020 Sergio Correia <scorreia@redhat.com> - 14-4
 - Backport upstream PR#230 - clevis-luks-askpass now exits cleanly
   when receives a SIGTERM