contrib, system: convert the shipped .conf files to the block format

The examples people copy from were still written in the line-based
format, so the block format was documented but nowhere demonstrated.

Two names in contrib were accidents of the old format, where the
service name falls out of the command basename: the Alpine and Void
keymap task was called zcat, and Debian's console/keyboard setup tasks
carried a .sh suffix.  They now carry the name their file implies.
Nothing referenced the old names.

The mdevd coldplug path keeps the name it has always had.  Its legacy
line spelled the name inside the cgroup argument, where it names the
cgroup leaf and not the service, so the barrier condition really is
<run/mdevd-coldplug/success> and not the <run/coldplug/success> the
comment above it promises.  Converted as-is so boot ordering does not
change; the discrepancy is now written down where it happens.

A list may not contain comments, the lexer sees the entries after the
'#' regardless:

    modules = {
    #	"fbcon",
    	"softdog"
    }

so the commented-out module candidates sit above the list instead.

setup-sysroot.sh removes 10-hotplug.conf from the test sysroot, so that
file is covered by parsing only, not by make check.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

contrib/void/finit.d/available/modules.conf

@@ -1,7 +1,3 @@
 ## Linux kernel modules to load
-#module fbcon
-#module button
-#module evdev
-#module mousedev
-#module 8139cp
-module softdog
+# Other candidates: fbcon, button, evdev, mousedev, 8139cp
+modules = { "softdog" }