Fix NullPointerException due plugin instance for jedis tasks in UUIDTranslator/AbstractDataManager

[AlessioDP]

Fixes the issue:

[19:09:29 ERROR]: Caused by: java.lang.NullPointerException: Cannot invoke "com.imaginarycode.minecraft.redisbungee.api.RedisBungeePlugin.isOnlineMode()" because "this.plugin" is null
[19:09:29 ERROR]:       at com.imaginarycode.minecraft.redisbungee.api.util.uuid.UUIDTranslator$2.unifiedJedisTask(UUIDTranslator.java:159)
[19:09:29 ERROR]:       at com.imaginarycode.minecraft.redisbungee.api.util.uuid.UUIDTranslator$2.unifiedJedisTask(UUIDTranslator.java:138)
[19:09:29 ERROR]:       at com.imaginarycode.minecraft.redisbungee.api.tasks.RedisTask.execute(RedisTask.java:56)
[19:09:29 ERROR]:       at com.imaginarycode.minecraft.redisbungee.api.util.uuid.UUIDTranslator.getNameFromUuid(UUIDTranslator.java:184)
[19:09:29 ERROR]:       at com.imaginarycode.minecraft.redisbungee.AbstractRedisBungeeAPI.getNameFromUuid(AbstractRedisBungeeAPI.java:316)
[19:09:29 ERROR]:       at com.imaginarycode.minecraft.redisbungee.AbstractRedisBungeeAPI.getNameFromUuid(AbstractRedisBungeeAPI.java:299)
...

In UUIDTranslator the plugin was initializing a RedisTask without passing the right plugin instance. new RedisTask<UUID>(plugin.getAbstractRedisBungeeApi()) -> new RedisTask<UUID>(plugin) For this reason, the plugin variable inside RedisTask was not correctly initialized.

In some unifiedJedisTask methods, the variable plugin is used, this behavior throws a NullPointerException, for example in the error above:

RedisTask<String> redisTask = new RedisTask<String>(plugin.getAbstractRedisBungeeApi()) {
    @Override
    public String unifiedJedisTask(UnifiedJedis unifiedJedis) {
        // ...

        if (!expensiveLookups || !plugin.isOnlineMode()) // <- Here the NullPointerException
            return null;
        // ...
    }
};