[17.0][FIX] dbs value has to be kept in case of special proxy config

[cvinh]

Same as #2828

[matmicro]

I propose a change into the OCA module dbfilter_from_header.

The change is to replace the line:
https://github.com/OCA/server-tools/blob/16.0/dbfilter_from_header/override.py:20

dbs = [db for db in dbs if re.match(db_filter_hdr, db)]
And replace it by:

dbs = [db for db in dbs_orig if re.match(db_filter_hdr, db)]
This change will allow to combine dbfilter_from_header AND the basic dbfilter.
This is really useful the generate some powerful regex like:

dbfilter = ^prod_\w+
dbfilter_from_header = \w+_%d$

Or maybe this commit is a regression that was introduced, and do not allow anymore to use both filters at the same time: @cvinh
e39ed29

[hbrunn]

see #3694 (review)