force dhcp.client to update /etc/resolv.conf

dhcp.client writes nameserver ip address to resolv.conf ONLY IF nameserver
entry does NOT exist in resolv.conf.
and dhcp.client ONLY write to resolv.conf once when it first starts.

this is unacceptable behavior since nameserver ipaddress can be changed or
resolv.conf can be corrupted or missing, then any sub-sequent
functions depends on resolv.conf will fail.

is there a way to force dhcp.client update /etc/resolv.conf ?