Fix BlobAccessToken expiration check

[vitoreiji]

Simple fixes that should alleviate the problem.

does not close but is related to #5153

Test notes

• Open the network tab on dev tools and then upload an attachment
• Verify that a BlobAccessToken was requested
• Note down the expiration time for the token (you can see it by looking at the response of the request, it is the expires property. Create a new Date() with this number to see the actual time)
• Create another blob attachment and see that no BlobAccessToken was requested
• Create another blob attachment 20 seconds before the expiration time of the first one and see that another token was requested.