codegen codecs for nomad structs

`ls *[!_test].go` was ignoring any file that ends with `s.go` (or any of
the letter inside `[]`), including `structs.go`!

nomad/structs/generate.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
 set -e
 
-FILES="$(ls *[!_test].go | tr '\n' ' ')"
+FILES="$(ls ./*.go | grep -v -e _test.go -e .generated.go | tr '\n' ' ')"
 codecgen -d 100 -o structs.generated.go ${FILES}