fstab-generator: extra dependencies specified in fstab should be applied to the mount...

fstab-generator: extra dependencies specified in fstab should be applied to the mount unit

If an entry in fstab uses "x-systemd.automount" option and also asks for
additionnal dependencies via x-systemd.requires or such, then the dependencies
were applied to the automount unit.

But this unlikely to do the right thing and is inconsistent with what's done
for network mounts.

Indeed when an fstab entries has "_netdev,x-systemd.automount" options, the
dependencies against the network requested by "_netdev" are (correctly) applied
to the mount unit only and the automount unit remains ordered against
local-fs.target.

The same logic should be followed when extra deps are specified via the mount
options as automount units should always be ordered against local-fs.target.

Note: in general explicit deps specified via mount options should be used with
care and should be used to specify dependencies on other mount units only as it
can easily create ordering cycles otherwise like it's been seen in
https://github.com/systemd/systemd-stable/issues/69. Mount units (as well as
automount ones) are ordered before local-fs.target by default which is a
low-level target that most other units depend on.

(cherry picked from commit 045c5faf5a3ef51cd39f738694e06c11a73f54b7)