test_classes: Modify functions to deal with web-public streams.
test_classes: Modify functions to deal with web-public streams.

Modify common_subscribe_to_streams to perform subscription in
web-public streams as well, and make_stream function to create
web-public streams.

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