sysv init scripts: use symbolic names in trap command

Not really necessary(*), but checkbashisms complains about
"trap with signal numbers".

(*) Quoting man 1p trap:
   trap [action condition...]
   [...]
   The condition can be EXIT, 0 (equivalent to EXIT),
   or a signal specified using a symbolic name, without the SIG prefix
   [...]
   XSI-conformant systems also allow numeric signal numbers[...]

Only one file is affected by this commit, and it should be checked
whether it really needs to ignore SIGTERM/SIGHUP or if the trap commands
can simply be removed:

 package/proftpd/S50proftpd

Signed-off-by: André Erdmann <dywi@mailerd.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/proftpd/S50proftpd

@@ -1,8 +1,8 @@
-#!/bin/sh 
+#!/bin/sh
 
 DAEMON=/usr/sbin/proftpd
-trap "" 1
-trap "" 15
+trap "" HUP
+trap "" TERM
 test -f $DAEMON || exit 0
 [ ! -d /var/run/proftpd ] && mkdir /var/run/proftpd
 [ ! -f /var/log/wtmp ] && touch /var/log/wtmp