block(d): always call hotplug.d "mount" scripts from blockd

block(d): always call hotplug.d "mount" scripts from blockd

This resolves problem on boot with "mount" scripts being called too
early to get blockd info. With this change "mount" scripts won't get
called until blockd starts. On startup it requests all devices info and
calls relevant scripts.

This fixes samba36-hotplug package hotplug.d script.

One downside of this change is handling "mount" evens on block restart
or crash. On restart "add" actions will get executed for mounted /
available (autofs) devices. On crash no events will be generated.

Ref: http://lists.infradead.org/pipermail/openwrt-devel/2019-December/020886.html
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>