Revert "build: add --with-jansson"

This reverts commit 12b34f0.

Jansson cannot parse QEMU's quirky JSON.
Revert back to yajl.

https://bugzilla.redhat.com/show_bug.cgi?id=1614569

Conflicts:
  configure.ac:
    Commit 8aa85e0 introduced LIBVIRT_*_LIBISCSI macros.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

configure.ac

@@ -250,7 +250,6 @@ LIBVIRT_ARG_FIREWALLD
 LIBVIRT_ARG_FUSE
 LIBVIRT_ARG_GLUSTER
 LIBVIRT_ARG_HAL
-LIBVIRT_ARG_JANSSON
 LIBVIRT_ARG_LIBISCSI
 LIBVIRT_ARG_LIBPCAP
 LIBVIRT_ARG_LIBSSH
@@ -292,7 +291,6 @@ LIBVIRT_CHECK_FUSE
 LIBVIRT_CHECK_GLUSTER
 LIBVIRT_CHECK_GNUTLS
 LIBVIRT_CHECK_HAL
-LIBVIRT_CHECK_JANSSON
 LIBVIRT_CHECK_LIBISCSI
 LIBVIRT_CHECK_LIBNL
 LIBVIRT_CHECK_LIBPARTED
@@ -978,7 +976,6 @@ LIBVIRT_RESULT_FUSE
 LIBVIRT_RESULT_GLUSTER
 LIBVIRT_RESULT_GNUTLS
 LIBVIRT_RESULT_HAL
-LIBVIRT_RESULT_JANSSON
 LIBVIRT_RESULT_LIBISCSI
 LIBVIRT_RESULT_LIBNL
 LIBVIRT_RESULT_LIBPCAP