Resource proxy fails if HEAD responds with 403

[brew]

Similar to #2412. Some servers[1] respond with a 403 to the initial HEAD request made by the resource_proxy extension[2], so don't attempt the GET request of the file.

[1]e.g. https://barnet.gov.uk/dam/jcr:7e9d19d0-071a-4209-9955-68485a5c937a/CSG_Overview_v0.2.pdf
[2]

ckan/ckanext/resourceproxy/controller.py

Lines 42 to 48 in 5304409

	r = requests.head(url)
	# 405 would be the appropriate response here, but 400 with
	# the invalid method mentioned in the text is also possible (#2412)
	if r.status_code in (400, 405):
	r = requests.get(url, stream=True)
	did_get = True
	r.raise_for_status()

[amercader]

Merged and picked to 2.4