patch 8.0.1552: may leak file descriptors when executing job

Problem:    May leak file descriptors when executing job.
Solution:   Close more file descriptors. (Ozaki Kiichi, closes #2531)
diff --git a/src/os_unix.c b/src/os_unix.c
index 59fe77a..ac89955 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -4601,6 +4601,12 @@
 	    reset_signals();		/* handle signals normally */
 	    UNBLOCK_SIGNALS(&curset);
 
+# ifdef FEAT_JOB_CHANNEL
+	    if (ch_log_active())
+		/* close the log file in the child */
+		ch_logfile((char_u *)"", (char_u *)"");
+# endif
+
 	    if (!show_shell_mess || (options & SHELL_EXPAND))
 	    {
 		int fd;
@@ -5454,6 +5460,12 @@
 	reset_signals();		/* handle signals normally */
 	UNBLOCK_SIGNALS(&curset);
 
+# ifdef FEAT_JOB_CHANNEL
+	if (ch_log_active())
+	    /* close the log file in the child */
+	    ch_logfile((char_u *)"", (char_u *)"");
+# endif
+
 # ifdef HAVE_SETSID
 	/* Create our own process group, so that the child and all its
 	 * children can be kill()ed.  Don't do this when using pipes,
@@ -5587,11 +5599,11 @@
     if (pty_master_fd >= 0)
 	close(pty_slave_fd); /* not used in the parent */
     /* close child stdin, stdout and stderr */
-    if (!use_file_for_in && fd_in[0] >= 0)
+    if (fd_in[0] >= 0)
 	close(fd_in[0]);
-    if (!use_file_for_out && fd_out[1] >= 0)
+    if (fd_out[1] >= 0)
 	close(fd_out[1]);
-    if (!use_out_for_err && !use_file_for_err && fd_err[1] >= 0)
+    if (fd_err[1] >= 0)
 	close(fd_err[1]);
     if (channel != NULL)
     {
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index 1859afc..9de3ca0 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -23,6 +23,21 @@
   call RunServer('test_channel.py', a:testfunc, a:000)
 endfunc
 
+" Return a list of open files.
+" Can be used to make sure no resources leaked.
+" Returns an empty list on systems where this is not supported.
+func s:get_resources()
+  let pid = getpid()
+
+  if has('mac')
+    return systemlist('lsof -p ' . pid . ' | awk ''$4~/^[0-9]*[rwu]$/&&$5=="REG"{print$NF}''')
+  elseif isdirectory('/proc/' . pid . '/fd/')
+    return systemlist('readlink /proc/' . pid . '/fd/* | grep -v ''^/dev/''')
+  else
+    return []
+  endif
+endfunc
+
 let g:Ch_responseMsg = ''
 func Ch_requestHandler(handle, msg)
   let g:Ch_responseHandle = a:handle
@@ -620,6 +635,7 @@
     call assert_equal(['line one', 'line two', 'this', 'AND this'], readfile('Xoutput'))
   finally
     call Stop_g_job()
+    call assert_equal(-1, match(s:get_resources(), '\(^\|/\)Xoutput$'))
     call delete('Xoutput')
   endtry
 endfunc
@@ -663,6 +679,7 @@
     call assert_equal(['line one', 'line two', 'this', 'AND this', 'that', 'AND that'], readfile('Xoutput'))
   finally
     call Stop_g_job()
+    call assert_equal(-1, match(s:get_resources(), '\(^\|/\)Xoutput$'))
     call delete('Xoutput')
   endtry
 endfunc
@@ -1662,6 +1679,7 @@
   call assert_equal("asdf\nasdf", getline(1))
   call assert_equal("xxx\n", getline(2))
   call assert_equal("\nyyy", getline(3))
+  call assert_equal(-1, match(s:get_resources(), '\(^\|/\)Xtestwrite$'))
 
   call delete('Xtestwrite')
   bwipe!
diff --git a/src/version.c b/src/version.c
index 389bbb1..48da8a3 100644
--- a/src/version.c
+++ b/src/version.c
@@ -779,6 +779,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1552,
+/**/
     1551,
 /**/
     1550,