patch 8.1.1624: when testing in the GUI may try to run gvim in a terminal

Problem:    When testing in the GUI may try to run gvim in a terminal.
Solution:   Add the -v argument. (Yee Cheng Chin, closes #4605)  Don't skip
            tests that work now.
diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index 53b7314..e1bb818 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -284,6 +284,13 @@
   return cmd
 endfunc
 
+" Get the command to run Vim, with --clean, and force to run in terminal so it
+" won't start a new GUI.
+func GetVimCommandCleanTerm()
+  " Add -v to have gvim run in the terminal (if possible)
+  return GetVimCommandClean() .. ' -v '
+endfunc
+
 " Run Vim, using the "vimcmd" file and "-u NORC".
 " "before" is a list of Vim commands to be executed before loading plugins.
 " "after" is a list of Vim commands to be executed after loading plugins.