oeqa/utils/httpserver: Rework to avoid hangs and improve logging

testimage.bbclass installs a SIGTERM handler which conflicts with the
use of multiprocessing here. This is paritcularly problematic if the http
service is terminated before its started and hence before its had a chance
to reset the default signal handler (as the code was written).

Instead, temporarily remove testimage's handler whilst forking the http process
which means the correct handler is installed and won't deadlock.

Also take the opportunity to add in some log messages about the server start
and shutdown so that future debugging is easier and its clearer what the code
is doing.

(From OE-Core rev: 0762b6021b87ceb1f37952f3a6d64a36e99ae6a5)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/runtime/cases/apt.py

@@ -18,7 +18,7 @@ class AptRepoTest(AptTest):
     @classmethod
     def setUpClass(cls):
         service_repo = os.path.join(cls.tc.td['DEPLOY_DIR_DEB'], 'all')
-        cls.repo_server = HTTPService(service_repo, cls.tc.target.server_ip)
+        cls.repo_server = HTTPService(service_repo, cls.tc.target.server_ip, logger=cls.tc.logger)
         cls.repo_server.start()
 
     @classmethod