DATAREDIS-988 - Consider transaction participation when releasing connections.

[mp911de]

We now check on connection release whether a connection is in MULTI state. If so, then we discard (rollback) the transaction to reset the connection to a fresh state.

We now consider RedisTemplate's enableTransactionSupport configuration when releasing connections. Previously, we released bound connections when being in a read-only transaction regardless of the configuration in RedisTemplate. This broke session callbacks that expected to remain on the same connection all but the first command were executed on a different connection.

Releasing a connection now no longer unbinds a connection if transaction support is disabled.

---

Related ticket: DATAREDIS-988.
Should be forward-ported.

[quaff]

Failed tests: 
  LettuceReactiveRedisConnectionUnitTests.multipleCallsInProgressShouldConnectOnlyOnce:171 
Wanted but not invoked:
connectionProvider.getConnection(
    interface io.lettuce.core.api.StatefulConnection
);
-> at org.springframework.data.redis.connection.lettuce.LettuceReactiveRedisConnectionUnitTests.multipleCallsInProgressShouldConnectOnlyOnce(LettuceReactiveRedisConnectionUnitTests.java:171)
Actually, there were zero interactions with this mock.

[quaff]

ping