Use correct ANSI control sequence compatible with watch (wookayin#32)

In some environments (Ubuntu 17.10), the control character sequence
for resetting colors/attributes (sgr0) can't be recognized in
watch command. As a result, an additional character may be shown.

Using different termstr seems to resolve this issue, in that
`term.normal` returns a compatible control sequence.

Author: wookayin

gpustat.py

@@ -385,7 +385,7 @@ def print_formatted(self, fp=sys.stdout, force_color=False, no_color=False,
             raise ValueError("--color and --no_color can't be used at the same time")
 
         if force_color:
-            t_color = Terminal(kind='linux', force_styling=True)
+            t_color = Terminal(kind='xterm-color', force_styling=True)
         elif no_color:
             t_color = Terminal(force_styling=None)
         else: