meta/scripts: python3: rename file -> open

file() API doesn't exist in python 3, convert to open(). Also handle
some cases where files aren't closed. Compatible with python 2.7.

[Contributions from Ed and Richard]

(From OE-Core rev: 0f4ec13e11bb8abe21aba2a28547dfb9372bc377)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/swabber-strace-attach

@@ -16,8 +16,8 @@ else:
     sys.exit()
 
 
-si = file(os.devnull, 'r')
-so = file(sys.argv[2], 'w')
+si = open(os.devnull, 'r')
+so = open(sys.argv[2], 'w')
 se = so
 
 # Replace those fds with our own