Make MAPPED_SCYLLA_VERSION a soft requirement

It is going to ease development and test process.
From now on if you want to run it on release you can just run it as
such:
SCYLLA_VERSION="6.0.2" pytest ....

Author: dkropachev

ci/run_integration_test.sh

@@ -36,6 +36,5 @@ ccm remove
 
 # run test
 
-export MAPPED_SCYLLA_VERSION=3.11.4
 PROTOCOL_VERSION=4  pytest -rf --import-mode append $*
 

tests/integration/__init__.py

@@ -185,10 +185,10 @@ def _get_dse_version_from_cass(cass_version):
     DSE_CRED = os.getenv('DSE_CREDS', None)
     CASSANDRA_VERSION = _get_cass_version_from_dse(DSE_VERSION.base_version)
     CCM_VERSION = DSE_VERSION.base_version
-else:  # we are testing against Cassandra or DDAC
+else:  # we are testing against Cassandra,DDAC or Scylla
     if SCYLLA_VERSION:
         cv_string = SCYLLA_VERSION
-        mcv_string = os.getenv('MAPPED_SCYLLA_VERSION', None)
+        mcv_string = os.getenv('MAPPED_SCYLLA_VERSION', '3.11.4') # Assume that scylla matches cassandra `3.11.4` behavior
     else:
         cv_string = os.getenv('CASSANDRA_VERSION', None)
         mcv_string = os.getenv('MAPPED_CASSANDRA_VERSION', None)