util.subp: do not attach stdin cloud-init's stdin to subprocesses (LP: 831505)

Fix issue where 'isatty' would return true for apt-add-repository.
It would get stdin which was attached to a terminal (/dev/console) and would
thus hang when running during boot.

This was done by changing all users of util.subp to have None input unless
input was given.  In that case, the input will be the string passed in.

ChangeLog

@@ -38,6 +38,11 @@
    * boothooks will now run more than once as they were intended (and as bootcmd
      commands do)
    * cloud-config and user-scripts will be updated from user data every boot
+ - Fix issue where 'isatty' would return true for apt-add-repository.
+   apt-add-repository would get stdin which was attached to a terminal
+  (/dev/console) and would thus hang when running during boot.  (LP: 831505)
+   This was done by changing all users of util.subp to have None input unless specified
+  
 0.6.1:
  - fix bug in fixing permission on /var/log/cloud-init.log (LP: #704509)
  - improve comment strings in rsyslog file tools/21-cloudinit.conf

cloudinit/CloudConfig/cc_apt_update_upgrade.py

@@ -127,7 +127,7 @@ def add_sources(srclist, searchList={ }):
 
         source=ent['source']
         if source.startswith("ppa:"):
-            try: util.subp(["add-apt-repository",source], "/dev/null")
+            try: util.subp(["add-apt-repository",source])
             except:
                 elst.append([source, "add-apt-repository failed"])
             continue

cloudinit/util.py

@@ -141,10 +141,8 @@ def runparts(dirp, skip_no_exist=True):
     return
 
 def subp(args, input=None):
-    s_in = None
+    sp = subprocess.Popen(args, stdout=subprocess.PIPE,
-    if input is not None:
+        stderr=subprocess.PIPE, stdin=subprocess.PIPE)
-        s_in = subprocess.PIPE
-    sp = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=s_in)
     out,err = sp.communicate(input)
     if sp.returncode is not 0:
         raise subprocess.CalledProcessError(sp.returncode,args, (out,err))