[SPARK-14799][SQL] Remove MetastoreRelation dependency from AnalyzeTable - part 1

## What changes were proposed in this pull request?
This patch isolates AnalyzeTable's dependency on MetastoreRelation into a single line. After this we can work on converging MetastoreRelation and CatalogTable.

## How was this patch tested?
Covered by existing tests.

Author: Reynold Xin <rxin@databricks.com>

Closes #12566 from rxin/SPARK-14799.