fix: Panic if Terraform fails installation

[kylecarbs]

Closes #1039.

[codecov]

Codecov Report

Merging #1056 (73b0170) into main (9faa39a) will increase coverage by 0.02%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##             main    #1056      +/-   ##
==========================================
+ Coverage   67.37%   67.40%   +0.02%     
==========================================
  Files         259      259              
  Lines       15061    15062       +1     
  Branches      152      152              
==========================================
+ Hits        10148    10152       +4     
+ Misses       3894     3890       -4     
- Partials     1019     1020       +1     

Flag	Coverage Δ
unittest-go-macos-latest	53.40% <75.00%> (-0.22%)	⬇️
unittest-go-postgres-	66.67% <75.00%> (+0.03%)	⬆️
unittest-go-ubuntu-latest	56.34% <75.00%> (-0.08%)	⬇️
unittest-go-windows-2022	53.03% <75.00%> (-0.02%)	⬇️
unittest-js	68.10% <ø> (ø)

Impacted Files	Coverage Δ
cli/start.go	63.36% <75.00%> (-0.15%)	⬇️
peerbroker/dial.go	77.04% <0.00%> (-6.56%)	⬇️
coderd/parameter/compute.go	74.07% <0.00%> (-4.45%)	⬇️
provisioner/echo/serve.go	54.40% <0.00%> (-2.40%)	⬇️
peer/conn.go	79.18% <0.00%> (-0.26%)	⬇️
coderd/database/queries.sql.go	83.65% <0.00%> (-0.21%)	⬇️
coderd/provisionerdaemons.go	62.95% <0.00%> (ø)
provisionerd/provisionerd.go	81.17% <0.00%> (+1.02%)	⬆️
peer/channel.go	87.28% <0.00%> (+4.04%)	⬆️
... and 2 more

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