BUILD: Fix build without ssh
    
    autoreconf -if
    ./configure --without-ssh
    make check
    
    src/tests/cmocka/test_utils-test_sss_ssh.o: In function `test_textual_public_key':
    src/tests/cmocka/test_sss_ssh.c:78: undefined reference to `sss_ssh_format_pubkey'
    src/tests/cmocka/test_sss_ssh.c:82: undefined reference to `sss_ssh_format_pubkey'
    src/tests/cmocka/test_sss_ssh.c:86: undefined reference to `sss_ssh_format_pubkey'
    src/tests/cmocka/test_sss_ssh.c:89: undefined reference to `sss_ssh_format_pubkey'
    src/tests/cmocka/test_sss_ssh.c:92: undefined reference to `sss_ssh_format_pubkey'
    src/tests/cmocka/test_utils-test_sss_ssh.o:src/tests/cmocka/test_sss_ssh.c:95:
        more undefined references to `sss_ssh_format_pubkey' follow
    collect2: error: ld returned 1 exit status
    
    Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>
    (cherry picked from commit d82ffa52dd4c3bb11115b1687edc189284797329)