test_events: Fix loop structure in settings test.
test_events: Fix loop structure in settings test.

The original commit was broken here:
b553507412352b516f55f4aae977ec23a237b206

The intention was to run the same loop for all
settings, but instead, we did a funny loop of
just resetting schema_checker, and then we only
actually tested the last value of the loop.

zulip/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,showell/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,punchagan/zulip,hackerkid/zulip,hackerkid/zulip,kou/zulip,kou/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,brainwane/zulip,eeshangarg/zulip,punchagan/zulip,punchagan/zulip,brainwane/zulip,zulip/zulip,rht/zulip,zulip/zulip,brainwane/zulip,punchagan/zulip,andersk/zulip,brainwane/zulip,eeshangarg/zulip,hackerkid/zulip,showell/zulip,punchagan/zulip,eeshangarg/zulip,punchagan/zulip,brainwane/zulip,andersk/zulip,rht/zulip,rht/zulip,brainwane/zulip,zulip/zulip,rht/zulip,showell/zulip,showell/zulip,zulip/zulip,zulip/zulip,andersk/zulip,punchagan/zulip,rht/zulip,hackerkid/zulip,zulip/zulip,hackerkid/zulip,rht/zulip,showell/zulip,showell/zulip,showell/zulip,eeshangarg/zulip,kou/zulip,hackerkid/zulip,kou/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,brainwane/zulip