Relax an eager sled agent assert - #10401

control: job assigned to worker 01M5DJBCGHNNMYVMWHXHA3D83N [factory aws, i-079792ae26e2c0c2b] (queued for 58 s)
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task: starting task 0: "setup"
task: process exited: duration 4084 ms, exit code 0
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task: starting task 1: "rust-toolchain"
task: process exited: duration 18448 ms, exit code 0
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task: starting task 2: "authentication"
task: process exited: duration 16 ms, exit code 0
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task: starting task 3: "clone repository"
task: process exited: duration 19744 ms, exit code 0
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task: starting task 4: "build"
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|  Documenting omicron-uuid-kinds v0.1.0 (/work/oxidecomputer/omicron/uuid-kinds)
|  Documenting dev-tools-common v0.1.0 (/work/oxidecomputer/omicron/dev-tools/common)
|     Finished `dev` profile [unoptimized + debuginfo] target(s) in 7m 37s
| warning: the following packages contain code that will be rejected by a future version of  [...]
| note: to see what the problems were, use the option `--future-incompat-report`, or run `ca [...]
|    Generated /work/oxidecomputer/omicron/target/doc/api_identity/index.html and 208 other  [...]
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| real     7:37.508790995
| user    14:24.776080889
| sys      3:50.123887780
| trap        0.182411723
| tflt        0.018196980
| dflt        0.063615333
| kflt        0.000096370
| lock  7:03:19.786527698
| slp   2:41:17.953147972
| lat        23.634861517
| stop     1:55.996805918
task: process exited: duration 831524 ms, exit code 0
|W| found 0 output files