sysroot user management postinsts: run with /bin/sh -e to report errors when they...

sysroot user management postinsts: run with /bin/sh -e to report errors when they happen

This exposes the following failure in a multilib setup, when everything
up to do_package_write_rpm is in sstate, but do_package_write_rpm is not
(there's a similar fail for lib64-man-db, and the failures themselves will be fixed separately
in the next commit):

Exception: subprocess.CalledProcessError: Command '/srv/storage/alex/yocto/build-multilib/tmp/work/x86_64-pokymllib64-linux/lib64-quilt/0.67/recipe-sysroot/usr/bin/postinst-base-passwd' returned non-zero exit status 1.

Subprocess output:
install: cannot stat '/srv/storage/alex/yocto/build-multilib/tmp/work/x86_64-pokymllib64-linux/lib64-quilt/0.67/lib64-recipe-sysroot/usr/share/base-passwd/passwd.master': No such file or directory

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>