rpc.tlsclntd, rpc.tlsservd: Fix getopt_long argument

The "C" option in the argument to getopt_long() was
missing a ":" for both rpc.tlsclntd.c and rpc.tlsservd.c.
This patch fixes this.

(cherry picked from commit 15881823b9dabbd9f561c4fa264fffc4f497b10c)