Eliminate shell param from subprocesses in tests

Of the calls to execute a subprocess performed in tests, none of them
require a shell. Test utility method was modified to not use a shell,
eliminating a discouraged practice.

Change-Id: If2571ee8f4ea2fdf6e14416d5abe5de275d3a1c4
Closes-Bug: 1348416

glance/tests/utils.py

@@ -282,13 +282,13 @@ def execute(cmd,
     path_ext = [os.path.join(os.getcwd(), 'bin')]
 
     # Also jack in the path cmd comes from, if it's absolute
-    executable = cmd.split()[0]
+    args = shlex.split(cmd)
+    executable = args[0]
     if os.path.isabs(executable):
         path_ext.append(os.path.dirname(executable))
 
     env['PATH'] = ':'.join(path_ext) + ':' + env['PATH']
-    process = subprocess.Popen(cmd,
-                               shell=True,
+    process = subprocess.Popen(args,
                                stdin=subprocess.PIPE,
                                stdout=subprocess.PIPE,
                                stderr=subprocess.PIPE,