sunrpc: Update show_svc_xprt_flags() to include recently added flags

XPT_KILL_TEMP was added by commit 546125d1 ("sunrpc: don't call
sleeping functions from the notifier block callbacks"), and
XPT_CONG_CTRL was added by commit 362142b2

 ("sunrpc: flag
transports as having congestion control") .

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>