Change from subprocess.call to Popen

In rprocess_plug_in_packages(), change from subprocess.call() to
subprocess.Popen(). This prevents child process from becoming orphans
when the parent process is terminated.

Change-Id: I7a31694de0985799042315843662f07570d2e8a3
Signed-off-by: Michael Walsh <micwalsh@us.ibm.com>
diff --git a/lib/gen_robot_plug_in.py b/lib/gen_robot_plug_in.py
index 035f1f7..0920067 100755
--- a/lib/gen_robot_plug_in.py
+++ b/lib/gen_robot_plug_in.py
@@ -141,8 +141,9 @@
             gp.print_timen("Processing " + call_point
                            + " call point programs.")
 
-    proc_plug_pkg_rc = subprocess.call(cmd_buf, shell=True,
-                                       executable='/bin/bash')
+    sub_proc = subprocess.Popen(cmd_buf, shell=True, executable='/bin/bash')
+    sub_proc.communicate()
+    proc_plug_pkg_rc = sub_proc.returncode
 
     if return_history:
         # Get the "Running" statements from the output.