Merge bitcoin/bitcoin#31614: test: expect that files may disappear from /proc/PID/fd/

b2e9fdc test: expect that files may disappear from /proc/PID/fd/ (Vasil Dimov)

Pull request description:

  `get_socket_inodes()` calls `os.listdir()` and then iterates on the results using `os.readlink()`. However a file may disappear from the directory after `os.listdir()` and before `os.readlink()` resulting in a `FileNotFoundError` exception.

  It is expected that this may happen for `bitcoind` which is running and could open or close files or sockets at any time. Thus ignore the `FileNotFoundError` exception.

ACKs for top commit:
  arejula27:
    ACK  [`b2e9fdc`](bitcoin/bitcoin@b2e9fdc)
  sipa:
    utACK b2e9fdc
  achow101:
    ACK b2e9fdc
  theuni:
    utACK b2e9fdc
  hodlinator:
    ACK b2e9fdc

Tree-SHA512: 8eb05393e4de4307a70af446c3fc7e8f7dc3f08bf9d68d74d02b0e4e900cfd4865249f297be31f1fd7b05ffea45eb855c5cfcd75704167950c1deb4f17109f33

Author: achow101

test/functional/test_framework/netutil.py

@@ -41,9 +41,12 @@ def get_socket_inodes(pid):
     base = '/proc/%i/fd' % pid
     inodes = []
     for item in os.listdir(base):
-        target = os.readlink(os.path.join(base, item))
-        if target.startswith('socket:'):
-            inodes.append(int(target[8:-1]))
+        try:
+            target = os.readlink(os.path.join(base, item))
+            if target.startswith('socket:'):
+                inodes.append(int(target[8:-1]))
+        except FileNotFoundError:
+            pass
     return inodes
 
 def _remove_empty(array):