Fixes some stability issues seen during route table update.

Fixes some stability issues seen during route table update.

Dont allow clean old_rtable until it's reference count is really 0.
Added more faster recognition for connect failure, so route table
update will not stuck in preparing new rtable while waiting, that
old_rtable reference count reaches 0.
"rtgate" lock is not needed to init and destroy continouosly.

Issue-ID: RIC-1020

Signed-off-by: Juha Hyttinen <juha.hyttinen@nokia.com>
Change-Id: Ia5a228679ef9e71634217405334a4b9dc2da01b7