Fix test case 180-fd-leaks when running on Fedora (#3911)

testcases/t/180-fd-leaks.t

@@ -29,6 +29,10 @@ my $tmp = tmpnam();
 mkfifo($tmp, 0600) or die "Could not create FIFO in $tmp";
 my ($outfh, $outname) = tempfile('/tmp/i3-ls-output.XXXXXX', UNLINK => 1);
 
+# Get fds from a clean shell
+my $shoutput = `sh -c "ls -l /proc/self/fd"`;
+
+# Get fds from i3
 cmd qq|exec ls -l /proc/self/fd >$outname && echo done >$tmp|;
 
 open(my $fh, '<', $tmp);
@@ -38,13 +42,16 @@ close($fh);
 unlink($tmp);
 
 # Get the ls /proc/self/fd output
-my $output;
+my $i3output;
 {
     local $/;
-    $output = <$outfh>;
+    $i3output = <$outfh>;
 }
 close($outfh);
 
+sub extract_fds {
+    my $output = @_;
+
     # Split lines, keep only those which are symlinks.
     my @lines = grep { /->/ } split("\n", $output);
 
@@ -55,12 +62,19 @@ delete $fds{0};
     delete $fds{1};
     delete $fds{2};
 
-# Filter out the fd which is caused by ls calling readdir().
+    # filter out the fd which is caused by ls calling readdir().
     for my $fd (keys %fds) {
         delete $fds{$fd} if $fds{$fd} =~ m,^/proc/\d+/fd$,;
     }
 
-is(scalar keys %fds, 0, 'No file descriptors leaked');
+    return %fds;
+}
+
+my %i3fds = extract_fds($i3output);
+my %shfds = extract_fds($shoutput);
+
+# Diff the fds to account for services that keep fds open, such as the System Security Services Daemon (sssd)
+is(scalar keys %i3fds, scalar keys %shfds, 'No file descriptors leaked');
 
 }