schema: nwfilter: Allow all accepted values for 'ipsetflags'
schema: nwfilter: Allow all accepted values for 'ipsetflags'

The parser for the 'ipsetflags' accepts the 'src' and 'dst' values
stripping case. Express the same in the schema to pass validation of any
accepted string.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

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