commands do not ignore TSTP if TSTP ignored already

[idallen]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu' 
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H   -I.  -I../bash -I../bash/include -I../bash/lib  
-D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat 
-Wformat-security -Werror=format-security -Wall
uname output: Linux idallen-oak.home.idallen.ca 3.13.0-37-generic 
#64~precise1-Ubuntu SMP Wed Sep 24 21:37:11 UTC 2014 x86_64 x86_64 x86_64 
GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.2
Patch Level: 25
Release Status: release

Description:

If a bash shell script starts up with TSTP ignored, commands run by that
script will not ignore TSTP, even if you set a trap in the script to
ignore TSTP.  If the script starts up with TSTP not ignored, then the
trap to ignore TSTP works fine.

Repeat-By:

Create these two scripts below one.sh and two.sh and run ./one.sh and use
^Z to signal TSTP.  The "sleep" will stop, even though TSTP is ignored.

Remove (comment out) the "trap" line from one.sh and run ./one.sh and
now ^Z (TSTP) is properly ignored when two.sh runs.

==> one.sh <==
    #!/bin/bash
    trap '' TSTP
    exec ./two.sh

==> two.sh <==
    #!/bin/bash
    trap '' TSTP
    while : ; do
        echo "DEBUG"
        sleep 1
    done