fix: Insert provisioner job logs async

[kylecarbs]

The context could be cancelled after a log is sent, which resulted
in a failure. This prevent's that from occurring by using the
background context.

Fixes this race: https://github.com/coder/coder/runs/5100325505?check_suite_focus=true#step:9:35

[codecov]

Codecov Report

Merging #185 (9415d81) into main (d55231c) will increase coverage by 2.43%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #185      +/-   ##
==========================================
+ Coverage   65.47%   67.90%   +2.43%     
==========================================
  Files         103      108       +5     
  Lines        5294     5631     +337     
  Branches       68       68              
==========================================
+ Hits         3466     3824     +358     
+ Misses       1498     1443      -55     
- Partials      330      364      +34     

Flag	Coverage Δ
unittest-go-macos-latest	65.68% <100.00%> (+0.10%)	⬆️
unittest-go-ubuntu-latest	67.28% <100.00%> (?)
unittest-go-windows-latest	65.25% <100.00%> (?)
unittest-js	64.66% <ø> (ø)

Impacted Files	Coverage Δ
coderd/provisionerdaemons.go	50.99% <100.00%> (+0.11%)	⬆️
provisioner/terraform/serve.go	68.75% <0.00%> (ø)
coderd/userpassword/userpassword.go	63.41% <0.00%> (ø)
database/postgres/postgres.go	70.73% <0.00%> (ø)
provisioner/terraform/parse.go	78.18% <0.00%> (ø)
provisioner/terraform/provision.go	75.69% <0.00%> (ø)
provisionerd/provisionerd.go	67.70% <0.00%> (+0.95%)	⬆️
peer/conn.go	78.71% <0.00%> (+1.02%)	⬆️
coderd/coderdtest/coderdtest.go	100.00% <0.00%> (+14.87%)	⬆️
database/migrate.go	52.38% <0.00%> (+52.38%)	⬆️
... and 1 more

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[bryphe-coder]

Nice catch 👍