node tests: Use zjquery in narrow.js.
node tests: Use zjquery in narrow.js.

Instead of custom stubs, we now use zjquery.  We also
limit a couple checks to the first call to
`show_empty_narrow_messages`, since it's the same
logic every time.

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