patch 8.2.1432: various inconsistencies in test files

Problem:    Various inconsistencies in test files.
Solution:   Add modelines where they were missing.  Use Check commands instead
            of silently skipping over tests.  Adjust indents and comments.
            (Ken Takata, closes #6695)
diff --git a/src/testdir/test_startup_utf8.vim b/src/testdir/test_startup_utf8.vim
index 1684d80..33f50a9 100644
--- a/src/testdir/test_startup_utf8.vim
+++ b/src/testdir/test_startup_utf8.vim
@@ -31,16 +31,14 @@
 endfunc
 
 func Test_read_fifo_utf8()
-  if !has('unix')
-    return
-  endif
+  CheckUnix
   " Using bash/zsh's process substitution.
   if executable('bash')
     set shell=bash
   elseif executable('zsh')
     set shell=zsh
   else
-    return
+    throw 'Skipped: bash or zsh is required'
   endif
   let linesin = ['ใƒ†ใ‚นใƒˆ', '€ÀÈÌÒÙ']
   call writefile(linesin, 'Xtestin')
@@ -80,3 +78,5 @@
   call StopVimInTerminal(buf)
   call delete('Xscript')
 endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab