Describe the problem

We have a roachtest hung on import seemingly due to an inability to acquire quota. This build is at 1ad0ecc.

In the logs we see:

ip-10-12-35-136> W190722 08:52:37.179946 146966 storage/quota_pool.go:108  [n3,s3,r4402/2:/Table/54/1/226{5/724…-6/763…}] have been waiting 1m0.000109892s attempting to acquire 1.0 MiB of proposal quota; acquired 1023 KiB so far

That 1MB number is the entirety of the proposal quota. Somehow we've lost some small amount. Likely this is due to either #38568 or #38343.