Fix proof storage clobber error for postgres backend #2807

Job	Run time
Docker build check	3m 14s
cross compilation	3m 49s
Format check	21s
Compilation check	37s
run itests	7m 17s
run itests postgres	14m 24s
Lint check	2m 19s
go mod check	20s
RPC check	1m 23s
Sqlc check	24s
test vector check	48s
run unit tests (unit-race)	6m 46s
run unit tests (unit-cover)	2m 27s
run unit tests (unit dbbackend=postgres)	4m 42s
	48m 51s

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