Bugfix: Restore border_style when restarting inplace (Thanks aniou)

Fixes #385.

testcases/t/61-regress-borders-restart.t

@@ -0,0 +1,39 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Regression test to check if borders are correctly restored after an inplace
+# restart.
+# found in eb8ad348b28e243cba1972e802ca8ee636472fc9
+#
+use X11::XCB qw(:all);
+use List::Util qw(first);
+use i3test;
+
+my $x = X11::XCB::Connection->new;
+my $i3 = i3("/tmp/nestedcons");
+my $tmp = fresh_workspace;
+my $window = open_standard_window($x);
+
+sub get_border_style {
+    my @content = @{get_ws_content($tmp)};
+    my $wininfo = first { $_->{window} == $window->id } @content;
+
+    return $wininfo->{border};
+}
+
+is(get_border_style(), 'normal', 'border style normal');
+
+cmd 'border 1pixel';
+
+is(get_border_style(), '1pixel', 'border style 1pixel after changing');
+
+# perform an inplace-restart
+cmd 'restart';
+
+sleep 0.25;
+
+does_i3_live;
+
+is(get_border_style(), '1pixel', 'border style still 1pixel after restart');
+
+done_testing;