[fix] Trim whitespace from pidfile content (#84)

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## Before this PR
We saw the below error in production:
```
failed to determine service status: failed to determine running processes: pid file did not contain an integer: strconv.Atoi: parsing "12773\n": invalid syntax
```

From reading the `Start` code I'm not sure how the newline got in there, but this should protect us from it in the future.

## After this PR
We will ignore spurious whitespace in the pidfile

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init/cli/lib.go

@@ -21,6 +21,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strconv"
+	"strings"
 	"syscall"
 
 	"github.com/palantir/pkg/cli"
@@ -102,7 +103,7 @@ func getCmdProcess(name string) (*int, *os.Process, error) {
 		return nil, nil, errors.Wrap(err, "failed to read pidfile")
 	}
 
-	pid, err := strconv.Atoi(string(pidBytes))
+	pid, err := strconv.Atoi(strings.TrimSpace(string(pidBytes)))
 	if err != nil {
 		return nil, nil, errors.Wrap(err, "pid file did not contain an integer")
 	}