### What changes were proposed in this pull request?
1. Remove UNKNOWN_DISK from StorageInfo.
2. Enable load-aware slots allocation when there is HDFS.
### Why are the changes needed?
To support the application's config about available storage types.
### Does this PR introduce _any_ user-facing change?
no.
### How was this patch tested?
GA and Cluster.
Closes#2098 from FMX/B1081-1.
Authored-by: mingji <fengmingxiao.fmx@alibaba-inc.com>
Signed-off-by: Shuang <lvshuang.tb@gmail.com>
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