Test-runner: provide a correct fix for SIGCHLD issue

Revert the yesterday's patch that installs SIGCHLD
handler to early collect <defunct> server processes
that received SIGSEGV/otherwise somehow terminated
abnormally.

The invinite loop in Tarantool_connection::recvall()
was caused by misuse of the Python socket API,
not by the fact that the sending side was still
"alive".

The correct fix simply checks for EOF received from
the other end and raises an exception if
we expected some data and got a EOF.

test/lib/tarantool_connection.py

@@ -125,6 +125,8 @@ class DataConnection(AdminConnection):
     res = ""
     while len(res) < length:
       buf = self.socket.recv(length - len(res))
+      if len(buf) == 0:
+        raise RuntimeError("recv(): The remote end has gone away")
       res = res + buf
     return res
 

test/lib/tarantool_silverbox_server.py

@@ -68,18 +68,6 @@ class TarantoolSilverboxServer:
     self.abspath_to_exe = None
     self.is_started = False
 
-    if self.args.gdb or self.args.start_and_exit:
-      self.sigchld_handler = signal.SIG_DFL
-    else:
-      def sigchld_handler(signo, frame):
-        os.wait3(os.WNOHANG)
-        print >>sys.stderr, "** The child has terminated abnormally: **"
-        traceback.print_stack(frame)
-        signal.signal(signal.SIGCHLD, sigchld_handler)
-
-      self.sigchld_handler = sigchld_handler
-
-
   def install(self, silent = False):
     """Start server instance: check if the old one exists, kill it
     if necessary, create necessary directories and files, start
@@ -139,11 +127,6 @@ class TarantoolSilverboxServer:
     if not silent:
       print "Starting {0} {1}.".format(os.path.basename(self.abspath_to_exe),
                                        version)
-  def setup_sigchld_handler(self):
-    signal.signal(signal.SIGCHLD, self.sigchld_handler)
-
-  def clear_sigchld_handler(self):
-    signal.signal(signal.SIGCHLD, signal.SIG_DFL)
 
   def start(self, silent = False):
 
@@ -185,8 +168,6 @@ class TarantoolSilverboxServer:
     else:
       wait_until_connected(self.suite_ini["host"], self.suite_ini["port"])
 
-    self.setup_sigchld_handler()
-
 # Set is_started flag, to nicely support cleanup during an exception.
     self.is_started = True
 
@@ -200,8 +181,6 @@ class TarantoolSilverboxServer:
         print "Stopping the server..."
       if self.args.gdb:
         self.kill_old_server(True)
-      else:
-        self.clear_sigchld_handler()
       self.server.terminate()
       self.server.expect(pexpect.EOF)
       self.is_started = False
@@ -215,12 +194,10 @@ class TarantoolSilverboxServer:
   def test_option(self, option_list_str):
     args = [self.abspath_to_exe] + option_list_str.split()
     print " ".join([os.path.basename(self.abspath_to_exe)] + args[1:])
-    self.clear_sigchld_handler()
     output = subprocess.Popen(args,
                           cwd = self.args.vardir,
                           stdout = subprocess.PIPE,
                           stderr = subprocess.STDOUT).stdout.read()
-    self.setup_sigchld_handler()
     print output