zdtm.py: ignore unicode encode errors

We have a problem after commit 212e4c771a1b ("test: make zdtm.py
python2/python3 compatible") when running tests on python2:

https://ci.openvz.org/job/CRIU/job/CRIU-virtuozzo/job/criu-dev/3804/console

Traceback (most recent call last):
  File "./test/zdtm.py", line 2249, in <module>
    opts['action'](opts)
  File "./test/zdtm.py", line 2001, in run_tests
    launcher.run_test(t, tdesc, run_flavs)
  File "./test/zdtm.py", line 1680, in run_test
    self.wait()
  File "./test/zdtm.py", line 1737, in wait
    self.__wait_one(0)
  File "./test/zdtm.py", line 1725, in __wait_one
    print(open(sub['log']).read())
UnicodeEncodeError: 'ascii' codec can't encode character u'\u2018' in
position 258: ordinal not in range(128)

print does not like "‘" symbol in zdtm_static_cgroup04.log:
...
rmdir: failed to remove ‘cgclean.sKFHLm/zdtmtst/special_prop_check’: No
such file or directory

Small reproducer:

[snorch@snorch ~]$ cat test_ascii.py
from __future__ import absolute_import, division, print_function, unicode_literals
from builtins import (str, open, range, zip, int, input)

f = open('./zdtm_static_cgroup04.log')
s = f.read()
print(s)

[snorch@snorch ~]$ python test_ascii.py | grep ""
Traceback (most recent call last):
  File "test_ascii.py", line 6, in <module>
    print(s)
UnicodeEncodeError: 'ascii' codec can't encode character u'\u2018' in
position 258: ordinal not in range(128)

So just ignore these quote symbol when printing logs.
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

test/zdtm.py

@@ -1622,7 +1622,7 @@ class Launcher:
 					print(testline, file=self.__file_report)
 
 			if sub['log']:
-				print(open(sub['log']).read())
+				print(open(sub['log']).read().encode('ascii', 'ignore'))
 				os.unlink(sub['log'])
 
 			return True