tests: Split the NSS db specific tests
If NSS is configured with NSS_DISABLE_DBM then Certmonger's tests
which are related to DBM fail. The legacy NSS db type(DBM) will be
eventually disabled. Thus, Certmonger should handle this.
NSS db specific tests are placed under the corresponding
HAVE_SQL_NSSDB and HAVE_DBM_NSSDB sections.
Fixes: https://pagure.io/certmonger/issue/155
Signed-off-by: Stanislav Levin <slev@altlinux.org>