greenio: Remove sendall-like semantincs from GreenSocket.send

When a socket timeout was set the sendall-like semantics was resulting
in losing information about sent data and raising socket.timeout exception.

The previous GreenSocket.send() implementation used to call fd.send() in a
loop until all data was sent. The issue would manifest if at least one
fd.send() call succeeded and was followed by a fd.send() call that would
block and a trampoline that timed out. The client code would see
socket.timeout being raised and would rightfully assume that no data was
sent which would be incorrect.

Discussed at https://github.com/eventlet/eventlet/issues/260.

eventlet/greenio/base.py

@@ -351,28 +351,20 @@ class GreenSocket(object):
         if self.act_non_blocking:
             return fd.send(data, flags)
 
-        # blocking socket behavior - sends all, blocks if the buffer is full
-        total_sent = 0
-        len_data = len(data)
         while 1:
             try:
-                total_sent += fd.send(data[total_sent:], flags)
+                return fd.send(data, flags)
             except socket.error as e:
                 eno = get_errno(e)
                 if eno == errno.ENOTCONN or eno not in SOCKET_BLOCKING:
                     raise
 
-            if total_sent == len_data:
-                break
-
             try:
                 self._trampoline(self.fd, write=True, timeout=self.gettimeout(),
                                  timeout_exc=socket.timeout("timed out"))
             except IOClosed:
                 raise socket.error(errno.ECONNRESET, 'Connection closed by another thread')
 
-        return total_sent
-
     def sendall(self, data, flags=0):
         tail = self.send(data, flags)
         len_data = len(data)