Revert "package/bash: add /bin/bash to /etc/shells"

Revert "package/bash: add /bin/bash to /etc/shells"

Commit 4d279697af added /bin/bash to /etc/shells. In the default
skeleton, however, /etc/shells doesn't exist, so in fact it creates
this file, containing only /bin/bash. Therefore, when bash is selected,
/bin/sh does not appear in /etc/shells and bash is the only shell
allowed. Since /bin/sh is the shell that is used for root in the
default skeleton's /etc/passwd, root is no longer able to log in.

The proper solution is to add all available shells to /etc/shells. For
now, however, just revert commit 4d279697af as a stop-gap measure. That
way, the default situation still works, and only people who update
/etc/passwd with additional logins but don't update /etc/shells will
suffer.

This reverts commit 4d279697afbf8fb295274784103be2b837113d5e.

Fixes: https://bugs.busybox.net/show_bug.cgi?id=10896
Cc: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Romain Naour <romain.naour@smile.fr>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>