BUG: fix the 'lower' attribute of dpotri to make dpotrf/dpotri consistent.
Should close gh-2691

Also remove (deprecated) clapack dpotri/dpotrf functions.
BUG: linalg: swap the logic in dpotri --- intent-c vs L/U

Also add some additional tests.
Merge pull request #2788 from EvgeniBurovski/dpotri__issue2691

BUG: linalg: fix the 'lower' attribute of dpotri to make dpotrf/dpotri consistent

Also remove (deprecated) clapack dpotri/dpotrf functions.

Fixes gh-2691