Remove unused pretest_clean.lua script

After the previous commit in the current patchset we don't use the same
tarantool server process from test to test and we don't need to use any
scripts like 'pretest_clean.lua' to cleanup it between tests. So this
patch removes this script.

Author: avtikhon

README.md

@@ -350,9 +350,8 @@ The behaviour of this option varies across test suite types (`core = tarantool /
 app / unittest`).
 
 For a `core = tarantool` test suite enabling of this option will lead to
-execution of a special clean function before each Lua test. The
-`pretest_clean.lua` file is copied into a test directory (`var/ddd-suite-name`)
-and `require('pretest_clean').clean()` is invoked before each test.
+execution of a special clean function `require('pretest_clean').clean()`
+before each Lua test.
 
 This function performs the following steps:
 

lib/tarantool_server.py

@@ -122,25 +122,6 @@ def write_result_file_version_line(self):
         sys.stdout.write(self.RESULT_FILE_VERSION_TEMPLATE.format(
                          self.result_file_version) + '\n')
 
-    def execute_pretest_clean(self, ts):
-        """ Clean globals, loaded packages, spaces, users, roles
-            and so on before each test if the option is set.
-
-            Return True as success (or if this feature is disabled
-            in suite.ini) and False in case of an error.
-        """
-        if not self.suite_ini['pretest_clean']:
-            return True
-
-        command = "require('pretest_clean').clean()"
-        result = self.send_command(command, ts, 'lua')
-        result = result.replace('\r\n', '\n')
-        if result != '---\n...\n':
-            sys.stdout.write(result)
-            return False
-
-        return True
-
     def execute_pragma_sql_default_engine(self, ts):
         """ Set default engine for an SQL test if it is provided
             in a configuration.
@@ -239,8 +220,6 @@ def flush(self, ts, command_log, command_exe):
 
     def exec_loop(self, ts):
         self.write_result_file_version_line()
-        if not self.execute_pretest_clean(ts):
-            return
         if not self.execute_pragma_sql_default_engine(ts):
             return
 
@@ -789,10 +768,6 @@ def copy_files(self):
         shutil.copy(tntctl_file, self.vardir)
         shutil.copy(os.path.join(self.TEST_RUN_DIR, 'test_run.lua'),
                     self.vardir)
-        # Need to use get here because of nondefault servers doesn't have ini.
-        if self.ini.get('pretest_clean', False):
-            shutil.copy(os.path.join(self.TEST_RUN_DIR, 'pretest_clean.lua'),
-                        self.vardir)
 
         if self.snapshot_path:
             # Copy snapshot to the workdir.