patch 8.0.1697: various tests are still a bit flaky

Problem:    Various tests are still a bit flaky.
Solution:   Increase the default wait time to five seconds.
diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index d47a355..6c3f8a4 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -113,14 +113,14 @@
   endif
 endfunc
 
-" Wait for up to a second for "expr" to become true.  "expr" can be a
+" Wait for up to five seconds for "expr" to become true.  "expr" can be a
 " stringified expression to evaluate, or a funcref without arguments.
 " A second argument can be used to specify a different timeout in msec.
 "
 " Return time slept in milliseconds.  With the +reltime feature this can be
 " more than the actual waiting time.  Without +reltime it can also be less.
 func WaitFor(expr, ...)
-  let timeout = get(a:000, 0, 1000)
+  let timeout = get(a:000, 0, 5000)
   " using reltime() is more accurate, but not always available
   if has('reltime')
     let start = reltime()