patch 8.0.0293: some tests have a one or three second wait

Problem:    Some tests have a one or three second wait.
Solution:   Reset the 'showmode' option.  Use a test time of one to disable
            sleep after an error or warning message.
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 430b89a..43192c4 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -57,9 +57,6 @@
   set encoding=latin1
 endif
 
-" Avoid stopping at the "hit enter" prompt
-set nomore
-
 " Output all messages in English.
 lang mess C
 
@@ -88,6 +85,14 @@
 
 function RunTheTest(test)
   echo 'Executing ' . a:test
+
+  " Avoid stopping at the "hit enter" prompt
+  set nomore
+
+  " Avoid a three second wait when a message is about to be overwritten by the
+  " mode message.
+  set noshowmode
+
   if exists("*SetUp")
     try
       call SetUp()