social_auth tests: Test registration with ldap populator enabled.
social_auth tests: Test registration with ldap populator enabled.

Finishes testing for the last remaining case and thus closes #13298.

rht/zulip,shubhamdhama/zulip,synicalsyntax/zulip,synicalsyntax/zulip,shubhamdhama/zulip,rht/zulip,shubhamdhama/zulip,rht/zulip,eeshangarg/zulip,showell/zulip,brainwane/zulip,showell/zulip,brainwane/zulip,kou/zulip,timabbott/zulip,timabbott/zulip,showell/zulip,zulip/zulip,andersk/zulip,rht/zulip,timabbott/zulip,brainwane/zulip,kou/zulip,eeshangarg/zulip,synicalsyntax/zulip,zulip/zulip,showell/zulip,hackerkid/zulip,rht/zulip,punchagan/zulip,shubhamdhama/zulip,andersk/zulip,showell/zulip,kou/zulip,synicalsyntax/zulip,rht/zulip,punchagan/zulip,synicalsyntax/zulip,andersk/zulip,eeshangarg/zulip,shubhamdhama/zulip,kou/zulip,kou/zulip,hackerkid/zulip,timabbott/zulip,andersk/zulip,andersk/zulip,shubhamdhama/zulip,zulip/zulip,punchagan/zulip,timabbott/zulip,showell/zulip,showell/zulip,hackerkid/zulip,eeshangarg/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,shubhamdhama/zulip,zulip/zulip,hackerkid/zulip,rht/zulip,zulip/zulip,punchagan/zulip,hackerkid/zulip,eeshangarg/zulip,zulip/zulip,punchagan/zulip,kou/zulip,zulip/zulip,hackerkid/zulip,brainwane/zulip,brainwane/zulip,punchagan/zulip,brainwane/zulip,synicalsyntax/zulip,hackerkid/zulip,punchagan/zulip,timabbott/zulip,brainwane/zulip,timabbott/zulip,andersk/zulip,eeshangarg/zulip,synicalsyntax/zulip