fix(resourceCache): patch #7151

[Will-ShaoHua]

Problem

97a4482

this commit breaks the cache by resetting the flag/lock on connection changed. When users sign in and have multiple VSCode instances, all windows will get a onConnectionChanged hence overwrite the lock/flag and load the resource from live.

Solution

Only clear the cache when users sign out, and it's sufficient for "change connection" use case as well. (users have to sign out before connecting with different connection)

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