strongswan: fix OpenWrt hotplug script handling

Commit 6cd8fcabe added ipsec hotplug script support by calling "exec
/sbin/hotplug-call ipsec".
Using the exec call breaks the insertion of iptables rules by the _updown.in
script as hotplug-call just replaces the current shell meaning the commands
following exec do not run since the shell is replaced and as a result lead to
connectivity issues.
Fix this by removing the exec command in front of /sbin/hotplug-call.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

net/strongswan/patches/300-include-ipsec-hotplug.patch

@@ -9,7 +9,7 @@
 +# This files/scripts are executed by the openwrt hotplug functionality on
 +# ipsec events.
 +
-+exec /sbin/hotplug-call ipsec "$1"
++/sbin/hotplug-call ipsec "$1"
 +
  #      PLUTO_VERSION
  #              indicates  what  version of this interface is being