patch 8.1.2281: 'showbreak' cannot be set for one window

Problem:    'showbreak' cannot be set for one window.
Solution:   Make 'showbreak' global-local.
diff --git a/src/testdir/test_breakindent.vim b/src/testdir/test_breakindent.vim
index 90c0ca5..ee61cbc 100644
--- a/src/testdir/test_breakindent.vim
+++ b/src/testdir/test_breakindent.vim
@@ -62,7 +62,8 @@
 
 func Test_breakindent02()
   " simple breakindent test with showbreak set
-  call s:test_windows('setl briopt=min:0 sbr=>>')
+  set sbr=>>
+  call s:test_windows('setl briopt=min:0 sbr=')
   let lines = s:screen_lines(line('.'),8)
   let expect = [
 	\ "    abcd",
@@ -122,7 +123,8 @@
 
 func Test_breakindent04()
   " breakindent set with min width 18
-  call s:test_windows('setl sbr= briopt=min:18')
+  set sbr=<<<
+  call s:test_windows('setl sbr=NONE briopt=min:18')
   let lines = s:screen_lines(line('.'),8)
   let expect = [
 	\ "    abcd",
@@ -132,6 +134,7 @@
   call s:compare_lines(expect, lines)
   " clean up
   call s:close_windows('set sbr=')
+  set sbr=
 endfunc
 
 func Test_breakindent04_vartabs()