test: enable parallel testing for vinyl suite

Need to switch on is_parallel flag for vinyl suite
to be able to run subtests in parallel using:
./test_run.py -j'<threads>'

Test vinyl/throttle.test.lua temporary disabled due
to it tests the performance which fails in parallel
runs because of highloaded hardware.

Fix #4158

test/vinyl/suite.ini

@@ -7,6 +7,7 @@ config = suite.cfg
 lua_libs = suite.lua stress.lua large.lua txn_proxy.lua ../box/lua/utils.lua
 use_unix_sockets = True
 long_run = stress.test.lua large.test.lua write_iterator_rand.test.lua dump_stress.test.lua select_consistency.test.lua throttle.test.lua
-is_parallel = False
-disabled = upgrade.test.lua
+is_parallel = True
+# throttle.test.lua temporary disabled for gh-4168
+disabled = upgrade.test.lua throttle.test.lua
 pretest_clean = True