MB-15761 generate cluster certificate with sha1 signature algoritm
MB-15761 generate cluster certificate with sha1 signature algoritm

...if appropriate internal setting is turned on, local certificate
will inherit the algorithm from the cluster cert

this is needed to support xdcr from 2.5 to 4.0, since 4.0 uses sha256,
but erlang14 used in 2.5 doesn't support it

Change-Id: I01c016bf0b66d72522f537bae10870770fcc6a5a
Reviewed-on: http://review.couchbase.org/53642
Tested-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

membase/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,ceejatec/ns_server