test(tvix/store): use tokio-retry for exp backoff

Rather than using this loop, use exponential backoff while waiting for
the socket path to be created.

Change-Id: I3056b1525784cd712b1d81f84876c9ca0be10dc6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9569
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI

tvix/store/Cargo.toml

@@ -77,6 +77,7 @@ tonic-build = "0.10.2"
 [dev-dependencies]
 test-case = "2.2.2"
 tempfile = "3.3.0"
+tokio-retry = "0.3.0"
 
 [features]
 default = ["fuse", "tonic-reflection"]