test_reactions: Cache stores reactions data after formatting.
test_reactions: Cache stores reactions data after formatting.

Reactions data should always be formatted before it saved in cache,
otherwise clients receive malformed data.

This is followup on a53daa6f8c7cb06ea4119a3e7c4063a47e2e7c41

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