dhcpcd: Remove option rapid_commit from dhcpcd.conf

Apparently some ISPs report they support it by sending the option
back, but the reality is they don't.

Fixes #499.

Author: rsmarples

src/dhcpcd.conf

@@ -34,11 +34,6 @@ option host_name
 # Most distributions have NTP support.
 #option ntp_servers
 
-# Rapid commit support.
-# Safe to enable by default because it requires the equivalent option set
-# on the server to actually work.
-option rapid_commit
-
 # A ServerID is required by RFC2131.
 require dhcp_server_identifier