rpm/fedora-2x/spec: enable TasksMax in service file

Since systemd version 228, a new setting, `TasksMax`, has appeared, which
limits the number of tasks used by a service (via pids cgroup
controller). Unfortunately, a default for this setting, `DefaultTaskMax`,
is set to 512. In systemd version 231 it is changed to 15% which
practically is 4195, as the value from /proc/sys/kernel/pid_max is
treated like 100%).

Either 512 or 4195 is severily limited value for Docker Engine, as it
can run thousands of containers with thousands of tasks in each, and
the number of tasks limit should be set on a per-container basis by the
Docker user. So, the most reasonable setting for `TasksMax` is `unlimited`.

Unfortunately, older versions of systemd warn about unknown `TasksMax`
parameter in `docker.service` file, and the warning is rather annoying,
therefore this setting is commented out by default, and is supposed to
be uncommented by the user.

The problem with that is, once the limit is hit, all sorts of bad things
happen and it's not really clear even to an advanced user that this
setting is the source of issues.

As Fedora 25 ships systemd 231, it (and later Fedora releases) support
TasksMax, so it makes total sense to uncomment the setting, this is what
this commit does.

Signed-off-by: Kir Kolyshkin <[email protected]>

rpm/fedora-26/docker-ce.spec

@@ -102,6 +102,8 @@ install -p -m 644 engine/contrib/udev/80-docker.rules $RPM_BUILD_ROOT/%{_sysconf
 install -d $RPM_BUILD_ROOT/etc/sysconfig
 install -d $RPM_BUILD_ROOT/%{_initddir}
 install -d $RPM_BUILD_ROOT/%{_unitdir}
+# Fedora 25+ supports (and needs) TasksMax
+sed -i 's/^#TasksMax=/TasksMax=/' /systemd/docker.service
 install -p -m 644 /systemd/docker.service $RPM_BUILD_ROOT/%{_unitdir}/docker.service
 # add bash, zsh, and fish completions
 install -d $RPM_BUILD_ROOT/usr/share/bash-completion/completions

rpm/fedora-27/docker-ce.spec

@@ -103,6 +103,8 @@ install -p -m 644 engine/contrib/udev/80-docker.rules $RPM_BUILD_ROOT/%{_sysconf
 install -d $RPM_BUILD_ROOT/etc/sysconfig
 install -d $RPM_BUILD_ROOT/%{_initddir}
 install -d $RPM_BUILD_ROOT/%{_unitdir}
+# Fedora 25+ supports (and needs) TasksMax
+sed -i 's/^#TasksMax=/TasksMax=/' /systemd/docker.service
 install -p -m 644 /systemd/docker.service $RPM_BUILD_ROOT/%{_unitdir}/docker.service
 # add bash, zsh, and fish completions
 install -d $RPM_BUILD_ROOT/usr/share/bash-completion/completions