patch 8.0.0916: cannot specify properties of window for terminal open

Problem:    Cannot specify properties of window for when opening a window for
            a finished terminal job.
Solution:   Add "term_opencmd".
diff --git a/src/testdir/test_terminal.vim b/src/testdir/test_terminal.vim
index 97c13ef..4de853a 100644
--- a/src/testdir/test_terminal.vim
+++ b/src/testdir/test_terminal.vim
@@ -320,7 +320,7 @@
 
 endfunc
 
-func Test_finish_close()
+func Test_finish_open_close()
   call assert_equal(1, winnr('$'))
 
   if s:python != ''
@@ -371,6 +371,19 @@
   call WaitFor("winnr('$') == 2", waittime)
   call assert_equal(2, winnr('$'))
   bwipe
+
+  call assert_fails("call term_start(cmd, {'term_opencmd': 'open'})", 'E475:')
+  call assert_fails("call term_start(cmd, {'term_opencmd': 'split %x'})", 'E475:')
+  call assert_fails("call term_start(cmd, {'term_opencmd': 'split %d and %s'})", 'E475:')
+  call assert_fails("call term_start(cmd, {'term_opencmd': 'split % and %d'})", 'E475:')
+
+  call term_start(cmd, {'term_finish': 'open', 'term_opencmd': '4split | buffer %d'})
+  close
+  call WaitFor("winnr('$') == 2", waittime)
+  call assert_equal(2, winnr('$'))
+  call assert_equal(4, winheight(0))
+  bwipe
+
 endfunc
 
 func Test_terminal_cwd()