pkg/server: enable active connection with graceful restart
pkg/server: enable active connection with graceful restart

No reason why active connection with graceful restart is disabled.

Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

osrg/gobgp,a16/gobgp,j-kato/gobgp,osrg/gobgp,a16/gobgp,a16/gobgp,fujita/gobgp,a16/gobgp,tamihiro/gobgp,osrg/gobgp,a16/gobgp,a16/gobgp,j-kato/gobgp,osrg/gobgp,tamihiro/gobgp,a16/gobgp,fujita/gobgp,tamihiro/gobgp,tamihiro/gobgp,fujita/gobgp,fujita/gobgp,j-kato/gobgp