Fix changing savedir directory mode

Commit 9f5764dac39b ("saveconfig: set right perms on /etc/target/ dir")
fixed CVE-2020-13867 by ensuring that the mode of the target
meta-data directory (/etc/target) was always mode 0600. But users
can specify a different directory, such as "/tmp", and we don't
want targetcli changing the mode of such directories to 0600. So
only change the mode of the directory, when saving a config file,
if the directory is /etc/target.

targetcli: avoild Ctrl+C print error stack

fix setting preference rollback error

Signed-off-by: Mingzhe Zou <zoumingzhe@qq.com>

Setting preference maybe rollback when execute multiple targetcli requests concurrently.
ConfigShell always initialization new Console object.
However, the lockfile need to be opened before requesting flock.
At this time, an exception may occur and need to be output to the console.
Currently, ConfigShell always initializes a new Console object.
So, ConfigShell is initialized first to be able to print information.
The prefs.bin file will be loaded when ConfigShell is initialized.
In this case, the old value may be read, if a new preference is being set and not saved.
In order to solve this problem we must first initialize a Console object.

This patch needs https://github.com/open-iscsi/configshell-fb/pull/62 to be merged first.

Signed-off-by: Zou Mingzhe <mingzhe.zou@easystack.cn>

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>

fileio backstore: fix sparse file creation

fallocate() can't be used to create sparse files because it
actually preallocates all the disk space that will be used by the file
backstore, sparse files do not have preallocated disk space
by definition.
We must therefore use ftruncate().

We can, on the other hand, use fallocate() to create non-sparse
files and fall back to the slower "while() fwrite()" if we
are running on Python version < 3.3 where fallocate() is not available

Fixes 3bd4d8ef7c9b154c53e8b8dd863a570bce7f5c2c

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>

Do not install systemd files in setup.py