[autogen.sh] support older git versions
[autogen.sh] support older git versions

older git version do not support 'git submodule update -i'

zbase/moxi,couchbase/moxi,couchbase/moxi,steveyen/moxi,membase/moxi,couchbase/moxi,steveyen/moxi,membase/moxi,membase/moxi,membase/moxi,couchbase/moxi,zbase/moxi,zbase/moxi,membase/moxi,couchbase/moxi,steveyen/moxi,zbase/moxi,steveyen/moxi,membase/moxi,steveyen/moxi,couchbase/moxi,zbase/moxi