usertools: fix telemetry client with python 3

usertools: fix telemetry client with python 3

When running the dpdk-telemetry-client.py with python 3, we get the
following syntax errors:

  File "usertools/dpdk-telemetry-client.py", line 70
      print "\nResponse: \n", str(data)
                           ^
  SyntaxError: invalid syntax

  File "usertools/dpdk-telemetry-client.py", line 93
      print "\nResponse: \n", str(data)
                           ^
  SyntaxError: invalid syntax

  File "usertools/dpdk-telemetry-client.py", line 111
      file_path = sys.argv[1]
                            ^
  TabError: inconsistent use of tabs and spaces in indentation

Import print_function from __future__ and add parentheses where missing.
Also, use spaces for indentation everywhere.

Fixes: d1b94da4a4e0 ("usertools: add client script for telemetry")
Fixes: 53f293c9a783 ("usertools: replace unsafe input function")
Fixes: 4080e46c8078 ("telemetry: support global metrics")
Cc: stable@dpdk.org
Signed-off-by: Robin Jarry <robin.jarry@6wind.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>