patch 8.0.1742: cannot get a list of all the jobs

Problem:    Cannot get a list of all the jobs.  Cannot get the command of
            the job.
Solution:   When job_info() is called without an argument return a list of
            jobs.  Otherwise, include the command that the job is running.
            (Yegappan Lakshmanan)
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index ce573f9..805fa8d 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -508,6 +508,16 @@
   let info = job_info(job)
   call assert_equal("dead", info.status)
   call assert_equal("term", info.stoponexit)
+  call assert_equal(2, len(info.cmd))
+  call assert_equal("test_channel_pipe.py", info.cmd[1])
+
+  let found = 0
+  for j in job_info()
+    if j == job
+      let found += 1
+    endif
+  endfor
+  call assert_equal(1, found)
 endfunc
 
 func Test_nl_pipe()