tcp_ratelimit: Handle some edge cases with TLS + RL send tags.

• After a connection has fallen back from NIC TLS to SW TLS, any pacing rate changes should modify the inpcb send tag even though SB_TLS_IFNET is set.

• If a connection tries to modify the pacing rate before the send tag has been converted from plain TLS to TLS + RL, don't fail the rate request set but let it fall through to setting the rate on the non-TLS inpcb RL tag.

Reviewed by: gallatin, rrs, hselasky
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D34085