Slf4j logs threadName incorrectly in some cases

I'm running Solr 8.6, and I'm seeing some logs report threadName with the entire log message and MDC. I haven't dug in too much, but CoreContainer logs seem to be the biggest culprit. Not sure if it's an issue of thread naming (including delimiter in name?), SolrLogFormat parsing, or something else altogether.

```

{ [    CoreAdminHandler.action: CREATE    CoreAdminHandler.asyncId: rebalance_replicas_trigger/41b16883a3bcTdzc5xqm9leudgekft79dpj5zl/372246269149506    collection: collectionName    core: collectionName_shard1_0_0_0_1_0_0_0_1_1_0_1_0_0_replica_s7606    level: INFO    logger: org.apache.solr.core.CoreContainer    message: Creating SolrCore 'collectionName_shard1_0_0_0_1_0_0_0_1_1_0_1_0_0_replica_s7606' using configuration from configset crm, trusted=true    node_name: REDACTED_HOSTNAME:8983_solr    replica: core_node7607    shard: shard1_0_0_0_1_0_0_0_1_1_0_1_0_0    threadId: 4861    *threadName: parallelCoreAdminExecutor-19-thread-6-processing-n:REDACTED_HOSTNAME:8983_solr x:collectionName_shard1_0_0_0_1_0_0_0_1_1_0_1_0_0_replica_s7606 t:Shared-932ac44c-06a4-44d3-ba8f-5a64c8f8d708 rebalance_replicas_trigger//41b16883a3bcTdzc5xqm9leudgekft79dpj5zl//372246269149506 CREATE*    timestamp: 2021-02-03T16:26:56.482Z    trace_id: Shared-932ac44c-06a4-44d3-ba8f-5a64c8f8d708 }

```