removed clear pem cache without R14 backwards compat
removed clear pem cache without R14 backwards compat

We had code that handled R14 that did not have
ssl_manager:clear_pem_cache function. We dropped support for R14 some
time ago, thus it's not needed anymore.

Change-Id: Ic5f5abcd2d6874e49297ebc0daa9562d91cce060
Reviewed-on: http://review.couchbase.org/46102
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

membase/ns_server,ceejatec/ns_server,mschoch/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server,mschoch/ns_server,mschoch/ns_server,membase/ns_server,mschoch/ns_server,nimishzynga/ns_server,ceejatec/ns_server,mschoch/ns_server,membase/ns_server,membase/ns_server,nimishzynga/ns_server,ceejatec/ns_server,membase/ns_server,nimishzynga/ns_server,membase/ns_server,nimishzynga/ns_server,mschoch/ns_server,nimishzynga/ns_server,nimishzynga/ns_server