The script runs with "set -e", as such `cmd && r=ok` seems wrong.
It worked apparently, but I don't understand why. Anyway, change
it.

Fixes: e64370341850 ('tests/client: run "test-client.py" also for meson')

This didn't help and was not necessary. Instead, there was an issue
that is fixed now.

This reverts commit b4c25f9131fd3eea47b9ca812d6049995fae017a.

See also commit 00e3fc036add ('clients/tests: ensure that we run nmcli
before client tests for LTO').

With the latest rework that code was dropped and tests (with LTO) are
broken as they hit a timeout (aside taking much longer).

Fixes: e64370341850 ('tests/client: run "test-client.py" also for meson')

We now get unit test failures hitting this timeout. That is
likely a new bug introduced somewhere, but to rule out that
the timeout is simply too short, increase it.

Note that "test-client.py" currently only tests nmcli. But what it does
is to spawn test-networkmanager-service.py and run nmcli against it.

As such, it could really be used to test any NetworkManager client
against the stub service. Hence this test is not under
"src/nmcli/tests", but under "src/tests/client/" where it is more
general.

Currently "src/" mostly contains the source code of the daemon.
I say mostly, because that is not true, there are also the device,
settings, wwan, ppp plugins, the initrd generator, the pppd and dhcp
helper, and probably more.

Also we have source code under libnm-core/, libnm/, clients/, and
shared/ directories. That is all confusing.

We should have one "src" directory, that contains subdirectories. Those
subdirectories should contain individual parts (libraries or
applications), that possibly have dependencies on other subdirectories.
There should be a flat hierarchy of directories under src/, which
contains individual modules.

As the name "src/" is already taken, that prevents any sensible
restructuring of the code.

As a first step, move "src/" to "src/core/". This gives space to
reorganize the code better by moving individual components into "src/".

For inspiration, look at systemd's "src/" directory.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/743

We want to move platform code to "shared/nm-platform". However, platform
code uses the logging infrastructure from the daemon, there is thus
an odd circular dependency.

Solve that by moving the "src/nm-logging.[hc]" to a new helper library
in "shared/nm-log-core".

"src/nm-logging.c" should be independent of libnm-core. It almost
is, except the error domain and code.

Move NM_MANAGER_ERROR to "nm-glib-aux/nm-shared-utils.h" so that
"nm-logging.c" is independent of libnm-core.