travis: fix collecting code coverage

The problem is in the chroot test:
geninfo: ERROR: /home/travis/build/xemul/criu/test/zdtm/static/chroot.dir.test/home/travis/build/xemul/criu/images/timer.gcno: could not open file

We can just ignore these errors.

travis-ci: success for travis: fix collecting code coverage
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

scripts/travis/travis-after_success

@@ -6,5 +6,5 @@ test -z "$GCOV" && exit 0
 
 sudo apt-get install -qq -y lcov
 gem install coveralls-lcov
-sudo lcov --directory ../.. --capture --output-file coverage.info
+sudo lcov --directory ../.. --capture --output-file coverage.info --ignore-errors graph
 coveralls-lcov coverage.info