make file trigger scriptlets not to fail in case systemd is unavailable

drop systemd dependency

man-db.spec

@@ -4,7 +4,7 @@
 Summary: Tools for searching and reading man pages
 Name: man-db
 Version: 2.7.6.1
-Release: 6%{?dist}
+Release: 7%{?dist}
 # GPLv2+ .. man-db
 # GPLv3+ .. gnulib
 License: GPLv2+ and GPLv3+
@@ -27,8 +27,6 @@ Provides: man-pages-reader = %{version}
 Provides: bundled(gnulib) = %{gnulib_ver}
 
 Requires: coreutils, grep, groff-base, gzip, less
-# for file trigger scriptlets
-Requires: systemd
 BuildRequires: systemd
 BuildRequires: gdbm-devel, gettext, groff, less, libpipeline-devel, zlib-devel
 BuildRequires: po4a, perl-interpreter, perl-version
@@ -114,11 +112,15 @@ fi
 
 # update cache
 %transfiletriggerin -- %{_mandir}
-/usr/bin/systemd-run /usr/bin/systemctl start man-db-cache-update
+if [ -x /usr/bin/systemd-run -a -x /usr/bin/systemctl ]; then
+    /usr/bin/systemd-run /usr/bin/systemctl start man-db-cache-update || :
+fi
 
 # update cache
 %transfiletriggerpostun -- %{_mandir}
-/usr/bin/systemd-run /usr/bin/systemctl start man-db-cache-update
+if [ -x /usr/bin/systemd-run -a -x /usr/bin/systemctl ]; then
+    /usr/bin/systemd-run /usr/bin/systemctl start man-db-cache-update || :
+fi
 
 
 %files -f %{name}.lang -f %{name}-gnulib.lang
@@ -172,6 +174,10 @@ fi
 %config(noreplace) %{_sysconfdir}/sysconfig/man-db
 
 %changelog
+* Thu Nov 16 2017 Nikola Forró <nforro@redhat.com> - 2.7.6.1-7
+- make file trigger scriptlets not to fail in case systemd is unavailable
+- drop systemd dependency
+
 * Wed Nov 08 2017 Nikola Forró <nforro@redhat.com> - 2.7.6.1-6
 - run cache update in a transient service using systemd-run
   resolves #1318058