iRules for SSL certificates

You need to use SSL::renegotiate and something like

when CLIENTSSL_HANDSHAKE {
  if { [SSL::cert count] > 0 } {
    if { $http_collected eq 1 } {
      HTTP::release
      set http_collected 0
    }
  }
} 
when HTTP_REQUEST {
  if { ([HTTP::host] eq "siteB.com") && ([HTTP::uri] starts_with "/admin/") } {
    if {[SSL::cert count] == 0} {
      set http_collected 1
      HTTP::collect
      SSL::session invalidate
      SSL::authenticate always
      SSL::authenticate depth 9
      SSL::cert mode require
      SSL::renegotiate enable
      SSL::renegotiate
    }
  }
}

Note: this is a modified example from the SSL::renegotiate page, and has not been tested, so YMMV