Don't retry infinitely many times on no output

[jyn514]

Example output:

[2020-07-06T22:29:20Z WARN  collector::execute] failed to deserialize stats, retrying (try 1); output: Output { status: ExitStatus(ExitStatus(0)), stdout: "", stderr: " Documenting issue-20936-deep-vector v0.1.0 (/tmp/.tmpeT8Qdq)\n    Finished dev [unoptimized + debuginfo] target(s) in 1.25s\n" }
[2020-07-06T22:29:21Z WARN  collector::execute] failed to deserialize stats, retrying (try 2); output: Output { status: ExitStatus(ExitStatus(0)), stdout: "", stderr: " Documenting issue-20936-deep-vector v0.1.0 (/tmp/.tmpeT8Qdq)\n    Finished dev [unoptimized + debuginfo] target(s) in 1.19s\n" }
[2020-07-06T22:29:22Z WARN  collector::execute] failed to deserialize stats, retrying (try 3); output: Output { status: ExitStatus(ExitStatus(0)), stdout: "", stderr: " Documenting issue-20936-deep-vector v0.1.0 (/tmp/.tmpeT8Qdq)\n    Finished dev [unoptimized + debuginfo] target(s) in 1.21s\n" }
[2020-07-06T22:29:23Z WARN  collector::execute] failed to deserialize stats, retrying (try 4); output: Output { status: ExitStatus(ExitStatus(0)), stdout: "", stderr: " Documenting issue-20936-deep-vector v0.1.0 (/tmp/.tmpeT8Qdq)\n    Finished dev [unoptimized + debuginfo] target(s) in 1.20s\n" }
thread 'main' panicked at 'failed to collect statistics after 5 tries', collector/src/bin/rustc-perf-collector/execute.rs:568:21

r? @Mark-Simulacrum

[jyn514]

I picked 5 tries arbitrarily, I can make it smaller or bigger if you like.

[jyn514]

Looks like a network failure? Or maybe someone deleted their repo?

 Preparing script-servo-2 (with Check)
[2020-07-06T22:35:59Z DEBUG collector::execute] "/home/runner/work/rustc-perf/rustc-perf/cache/0c03aee8b81185d65b5821518661c30ecdb42de5/bin/cargo" "rustc" "--manifest-path" "components/script/Cargo.toml" "-p" "file:///tmp/.tmpiUVNJ2/components/script#0.0.1" "--profile" "check" "--no-default-features" "--"
Failed to benchmark script-servo-2, recorded: expected success, got exit code: 101

stderr=    Updating git repository `https://github.com/servo/mio.git`
    Updating git repository `https://github.com/servo/surfman`
    Updating git repository `https://github.com/asajeffrey/surfman-chains`
error: failed to resolve patches for `https://github.com/rust-lang/crates.io-index`

Caused by:
  failed to load source for dependency `surfman-chains`

Caused by:
  Unable to update https://github.com/asajeffrey/surfman-chains#b949a240

Caused by:
  object not found - no match for id (b949a240d73ef86d3c4bd22bc3d93933fac21ee9); class=Odb (9); code=NotFound (-3)

[Mark-Simulacrum]

Yeah I haven't had time to look into that failure, it seems the commit does exist if I manually clone, not sure why Cargo isn't able to get at it.