chore(test-utils): improve handling of running docker containers (open-telemetry#1695)

- Convert the output of run commands to a string that is readable.
- No need to `docker rm ...` test containers for `npm run test:local` usage
  because the `docker run --rm ...` option will remove them when stopped.

Author: trentm

packages/opentelemetry-test-utils/src/test-utils.ts

@@ -60,23 +60,23 @@ export function startDocker(db: keyof typeof dockerRunCmds) {
 
 export function cleanUpDocker(db: keyof typeof dockerRunCmds) {
   run(`docker stop otel-${db}`);
-  run(`docker rm otel-${db}`);
 }
 
 function run(cmd: string) {
   try {
     const proc = childProcess.spawnSync(cmd, {
       shell: true,
     });
+    const output = Buffer.concat(
+      proc.output.filter(c => c) as Buffer[]
+    ).toString('utf8');
     if (proc.status !== 0) {
       console.error('Failed run command:', cmd);
-      console.error(proc.output);
+      console.error(output);
     }
     return {
       code: proc.status,
-      output: proc.output
-        .map(v => String.fromCharCode.apply(null, v as any))
-        .join(''),
+      output,
     };
   } catch (e) {
     console.log(e);