fdo#72277: don't build and use nsspem when building against system curl

System CURL will know how to get the CA bundle from the system openSSL.
There is no need to have internal NSS CA database support.

Change-Id: Ie5074c78f7d78b2c2f452d4d4e11c98222529883

Conflicts:
	ucb/source/ucp/cmis/cmis_content.cxx
	ucb/source/ucp/cmis/cmis_repo_content.cxx