serivice/bgp: Fix ssh connection problem in Python 2.7
serivice/bgp: Fix ssh connection problem in Python 2.7

Currently, 'is_connected' attribute in SshServer is refered
before it is created, in Python 2.7.
This raises an Exception and the SSH operation won't work
anymore after this happens.
This commit ensures that 'is_connected' is created before
it is refered.

Signed-off-by: Satoshi Fujimoto <cd75558e8cccb245feb2368a5a53f09e4ecc2257@gmail.com>
Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

lagopus/ryu-lagopus-ext,lagopus/ryu-lagopus-ext,iwaseyusuke/ryu,fujita/ryu,fujita/ryu,iwaseyusuke/ryu,iwaseyusuke/ryu,fujita/ryu,fujita/ryu,lagopus/ryu-lagopus-ext,osrg/ryu,fujita/ryu,lagopus/ryu-lagopus-ext,osrg/ryu,osrg/ryu,osrg/ryu,lagopus/ryu-lagopus-ext,iwaseyusuke/ryu,osrg/ryu,iwaseyusuke/ryu