internal/pkg: isolate container params

This enables exporting container params for interactive troubleshooting within the cure container.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/exec_test.go

@@ -92,7 +92,7 @@ func TestExec(t *testing.T) {
 					[]string{"testtool"},
 
 					pkg.ExecPath{},
-				), nil, pkg.Checksum{}, os.ErrInvalid},
+				), nil, pkg.Checksum{}, pkg.ErrInvalidPaths},
 			})
 
 			// check init failure passthrough