Fix bug when setting readonly room as default room

[alexbrazier]

@RocketChat/core

Closes #4405
Probably also closes #825 as this is now done

• Fix bug to mute users in default read only channels
• Show muted icon in members list to easily spot who is muted (already half implemented)

[alexbrazier]

Any ideas why the build keeps on failing when building rocketchat:cas?

rocketchat:cas: updating npm dependencies -- cas...

   Building package rocketchat:autolinker    \

   Building package rocketchat:cas           \

   Building package rocketchat:cas           \

   Building package rocketchat:cas           \

   Building package rocketchat:cas           \

Just logs Building package rocketchat:cas until it errors.

Seems to be doing it in general (nothing to do with these code changes)

[graywolf336]

@alexbrazier I haven't tested it out, but what does the chat box to type in look like when you're muted? I think it'd be nice if the chat box became disabled and the placeholder/text in it became "Chatting disabled, you have been muted." and the user couldn't type of click any of the buttons to do any actions.

@engelgabriel any idea why the build is failing in travis?

[alexbrazier]

Seems the build is now passing.
@graywolf336 this is what it looks like when you are muted in a read only room: