qemuMigrationCapsToJSON: Refactor capability object formatting
qemuMigrationCapsToJSON: Refactor capability object formatting

Use virJSONValueObjectCreate rather than creating the object
piece-by-piece and use new accessors for bitmap to simplify the code.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Jiri Denemark <62bdf77dc47919a4d59a91822129d14633cfca81@redhat.com>

zippy2/libvirt,nertpinx/libvirt,jardasgit/libvirt,zippy2/libvirt,libvirt/libvirt,nertpinx/libvirt,jardasgit/libvirt,libvirt/libvirt,jfehlig/libvirt,jfehlig/libvirt,nertpinx/libvirt,nertpinx/libvirt,libvirt/libvirt,crobinso/libvirt,zippy2/libvirt,olafhering/libvirt,olafhering/libvirt,crobinso/libvirt,jfehlig/libvirt,olafhering/libvirt,zippy2/libvirt,nertpinx/libvirt,jardasgit/libvirt,crobinso/libvirt,jardasgit/libvirt,libvirt/libvirt,jardasgit/libvirt,olafhering/libvirt,jfehlig/libvirt,crobinso/libvirt