Fix signal handler in daemon mode

- signal handler requires the main thread to run

src/bitmessagemain.py

@@ -27,6 +27,7 @@ import socket
 import ctypes
 from struct import pack
 from subprocess import call
+from time import sleep
 
 from api import MySimpleXMLRPCRequestHandler, StoppableXMLRPCServer
 from helper_startup import isOurOperatingSystemLimitedToHavingVeryFewHalfOpenConnections
@@ -315,6 +316,10 @@ class Main:
         else:
             BMConfigParser().remove_option('bitmessagesettings', 'dontconnect')
 
+        if daemon:
+            while state.shutdown == 0:
+                sleep(1)
+
     def daemonize(self):
         try:
             if os.fork():