Run pip freeze command as root

Else it throws error during installation
 ProcessExecutionError: Unexpected error while running command.
 Command: pip-python freeze --local
 Exit code: 1
 Stdout: 'The temporary folder for building (/tmp/pip-build-op_stack)
 is not owned by your user! pip will not work until the temporary folder
 is either deleted or owned by your user account.\n'
Note: op_stack is username with which this command is run
/tmp/pip-build-op_stack is actually owned by root, created during bootstrap

Change-Id: Id64b76c15ad33fd98784feaccb7c572eed1c4f0e