tools: Update tcpdrop error message when the probe fails
tools: Update tcpdrop error message when the probe fails

When tcpdrop tool fails to attach a kprobe to tcp_drop() function, the
error message suggest that the running kernel is too old. However,
tcp_drop() is a relatively small static function, so nowadays, it's
more likely that it has been inlined.

Update the error message to avoid to confuse the user.

Signed-off-by: Jerome Marchand <d3643b417d7bb29446cdadf5ebe2f94cac95db45@redhat.com>

iovisor/bcc,iovisor/bcc,iovisor/bcc,iovisor/bcc,iovisor/bcc