Load/unload kernel module on start/stop (#459)

* Load/unload kernel module on start/stop

When falco is started, load the kernel module. (The falco binary also
will do a modprobe if it can't open the inspector, as a backup).

When falco is stopped, unload the kernel module.

This fixes https://github.com/falcosecurity/falco/issues/418.

* Put script execute line in right place.

scripts/rpm/falco

@@ -1,3 +1,5 @@
+#!/bin/sh
+
 #
 # Copyright (C) 2016-2018 Draios Inc dba Sysdig.
 #
@@ -16,7 +18,6 @@
 # limitations under the License.
 #
 
-#!/bin/sh
 #
 # falco syscall monitoring agent
 #
@@ -53,6 +54,9 @@ start() {
     # [ -f $config ] || exit 6
     echo -n $"Starting $prog: "
     daemon $exec --daemon --pidfile=$pidfile
+    if [ ! -d /sys/module/falco_probe ]; then
+        /sbin/modprobe falco-probe || return $?
+    fi
     retval=$?
     echo
     [ $retval -eq 0 ] && touch $lockfile
@@ -64,6 +68,7 @@ stop() {
     killproc -p $pidfile
     retval=$?
     echo
+    /sbin/rmmod falco-probe
     [ $retval -eq 0 ] && rm -f $lockfile
     return $retval
 }