Disable pytest cacheprovider plugin in CI

The pytest "cacheprovider" plugin produces a .cache/v/cache/lastfailed
file, which holds a Python dictionary structure with failed tests.
However, on Ubuntu 16.04 (Xenial) the file is created even though the
test passed and the file contains just an empty dictionary ("{}").

Given that we are not interested in this feature, disabling the
"cacheprovider" plugin globally and removing per-test removals of the
.cache directory seems like the best course of action.

.gitlab-ci.yml

@@ -39,6 +39,10 @@ variables:
   # In multithreaded unit tests, abort on the first failure
   CMOCKA_TEST_ABORT: 1
 
+  # Disable pytest's "cacheprovider" plugin to prevent it from creating
+  # cross-testrun files as there is no need to use that feature in CI.
+  PYTEST_ADDOPTS: "-p no:cacheprovider"
+
   # Default platforms to run "stress" tests on
   BIND_STRESS_TEST_OS: linux
   BIND_STRESS_TEST_ARCH: amd64

bin/tests/system/.gitignore

@@ -1,3 +1,4 @@
+.cache
 __pycache__
 dig.out*
 rndc.out*

bin/tests/system/rpzextra/clean.sh

@@ -15,4 +15,3 @@ rm -f ns*/named.run
 rm -f ns*/rpz*.txt
 rm -rf __pycache__
 rm -f *.status
-rm -rf .cache

bin/tests/system/shutdown/clean.sh

@@ -15,4 +15,3 @@ rm -f */named.conf
 rm -f */named.run
 rm -rf __pycache__
 rm -f *.status
-rm -rf .cache

bin/tests/system/statschannel/.gitignore

@@ -1,2 +1 @@
-/.cache/
 /__pycache__/

bin/tests/system/statschannel/clean.sh

@@ -27,4 +27,4 @@ rm -f traffic traffic.out.* traffic.json.* traffic.xml.*
 rm -f xml.*mem json.*mem
 rm -f xml.*stats json.*stats
 rm -f zones zones.out.* zones.json.* zones.xml.* zones.expect.*
-rm -rf ./.cache ./__pycache__
+rm -rf ./__pycache__

bin/tests/system/timeouts/clean.sh

@@ -15,5 +15,5 @@ rm -f ./ns*/named.lock
 rm -f ./ns*/named.memstats
 rm -f ./ns*/named.run*
 rm -f ./ns*/named.stats
-rm -rf ./.cache ./__pycache__
+rm -rf ./__pycache__
 rm -f ./ns*/large.db