sysctl_msec_to_ticks is used with both virtualized and

sysctl_msec_to_ticks is used with both virtualized and
non-vrtiualized sysctls so we cannot used one common function.

Add a macro to convert the arg1 in the virtualized case to
vnet.h to not expose the maths to all over the code.

Add a wrapper for the single virtualized call, properly handling
arg1 and call the default implementation from there.

Convert the two over places to use the new macro.

Reviewed by:	rwatson
Approved by:	re (kib)