It is possible, for example, to configure both 10.1.0.3/32 and
10.1.0.3/24 on the same interface. When checking whether an address
deleted from an interface is one of our VIPs, we need to also check
the prefix length.

Signed-off-by: Quentin Armitage <[email protected]>

Prior to a config-check, the log file is truncated (to 0 size). If
/dev/null (or any other non-regular) file was specified, truncate()
gives error EINVAL, which was not being handled in the code.

This commit stops keepalived logging an error if the output file
specified (or the default /dev/null) is a character device.

Signed-off-by: Quentin Armitage <[email protected]>