Fix usage of fprintf() in bin/drydock command

Summary: See PHI513. `fprintf()` takes `(thing, pattern, args, ...)` but we aren't passing a `pattern`, so if the command returns a "%" in the output we get an error.

Test Plan:
  - Installed `bytes`, a great useful program which prints all the bytes, on my HoaxOS(tm) system (see D19102).

```
epriestley@orbital ~/dev/phabricator $ ./bin/drydock command --lease 76287 -- bytes # Before patch.
[2018-03-29 02:09:08] ERROR 2: fprintf(): Too few arguments at [/Users/epriestley/dev/core/lib/phabricator/src/applications/drydock/management/DrydockManagementCommandWorkflow.php:60]
arcanist(head=experimental, ref.master=b8c9c385a7f5, ref.experimental=925c60e7b837), corgi(head=master, ref.master=6371578c9d32), instances(head=master, ref.master=d983b9517924), ledger(head=master, ref.master=4da4a24b8779), libcore(), phabricator(head=hoax1, ref.master=b586ee065a75, ref.hoax1=f8d7480bbdd1, custom=4), phutil(head=master, ref.master=1ad42491e44a), secure(head=master, ref.master=988cf9bd7958), services(head=master, ref.master=6b3fb8d8dd0a)
  #0 fprintf(resource, string) called at [<phabricator>/src/applications/drydock/management/DrydockManagementCommandWorkflow.php:60]
  #1 DrydockManagementCommandWorkflow::execute(PhutilArgumentParser) called at [<phutil>/src/parser/argument/PhutilArgumentParser.php:441]
  #2 PhutilArgumentParser::parseWorkflowsFull(array) called at [<phutil>/src/parser/argument/PhutilArgumentParser.php:333]
  #3 PhutilArgumentParser::parseWorkflows(array) called at [<phabricator>/scripts/drydock/drydock_control.php:21]
epriestley@orbital ~/dev/phabricator $ ./bin/drydock command --lease 76287 -- bytes # After patch.

!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
```

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Differential Revision: https://secure.phabricator.com/D19264

src/applications/drydock/management/DrydockManagementCommandWorkflow.php

@@ -57,8 +57,8 @@ final class DrydockManagementCommandWorkflow
       array($interface, 'execx'),
       array('%Ls', $argv));
 
-    fprintf(STDOUT, $stdout);
-    fprintf(STDERR, $stderr);
+    fwrite(STDOUT, $stdout);
+    fwrite(STDERR, $stderr);
 
     return 0;
   }