iproto: disable feature discovery for specific versions

"IProto features" are available since Tarantool 2.10 and there is
no need to even try to fetch them for lower versions.
Such check there is in netbox code [1].
Before this patch cartridge remote control closed the connection
after RequestProtocolVersion however but for netbox it worked
fine.
So let's uniform behaviour between connectors adding a small check
to skip request if there is a gurarntee that "IProto features" are
not supported.

Closes tarantool#283

[1] tarantool/tarantool@2cbec82#diff-a47383908beda20a06c9f64bf5c3d4c51879034e38bcdccdf45210e89ce6dfb7R1947

Author: olegrok

Diff for: tarantool/connection.py

@@ -1014,7 +1014,8 @@ def handshake(self):
         if greeting.protocol != "Binary":
             raise NetworkError("Unsupported protocol: " + greeting.protocol)
         self.version_id = greeting.version_id
-        self._check_features()
+        if self.version_id >= version_id(2, 10, 0):
+            self._check_features()
         self.uuid = greeting.uuid
         self._salt = greeting.salt
         if self.user: