Database: Fix degenerate parenthesized joins

Database: Fix degenerate parenthesized joins

The SQL standard supports parenthesized joins like

    a JOIN (b JOIN c ON (...)) ON (...)

But it doesn't support parenthesizing a single table name, i.e. a
one-table "join", like

    a JOIN (b) ON (...)

Detect the degenerate single-table case and omit the parentheses.

Bug: T181674
Change-Id: I82cacd80465092aa67ff19bdcfd6682001bf12ab