Drizzlepac/HAP: Add log line in STWCS listing astrometry database link used

[stscijgbot-hstdp]

Issue HLA-1467 was created on JIRA by Steve Goldman:

At the request of Lisa, we should add a line in STWCS that prints out the astrometry database url that is being used. This should work the same whether a url is specified to AstromtryDB, or an environmental variable (e.g. ASTROMETRY_SERVICE_URL) is specified. 

This fix should be included in a new stwcs release, then a drizzlepac release, and then a new caldp build release candidate.