Increase the number of file descriptors for stress_http_quota.py

stress_http_quota.py uses more than 256 file descriptors and fails
on some platforms.  Increase the available descriptors to 1024.

bin/tests/system/doth/stress_http_quota.py

@@ -18,12 +18,20 @@ import random
 import time
 
 from functools import reduce
+from resource import getrlimit
+from resource import setrlimit
+from resource import RLIMIT_NOFILE
 
 MULTIDIG_INSTANCES = 10
 CONNECT_TRIES = 5
 
 random.seed()
 
+# Ensure we have enough file desriptors to work
+rlimit_nofile = getrlimit(RLIMIT_NOFILE)
+if rlimit_nofile[0] < 1024:
+    setrlimit(RLIMIT_NOFILE, (1024, rlimit_nofile[1]))
+
 
 # Introduce some random delay
 def jitter():