Fixes a regression in installation tests, whereby 'guix system init'
would report that virtio modules are missing for the target devices.
In practice virtio modules were always available since 'base-initrd' was
always called with #:virtio? #t. This commit simply moves them to
'%base-initrd-modules' so that 'guix system' knows they're available.
Reported by Danny Milosavljevic <dannym@scratchpost.org> at
<https://debbugs.gnu.org/cgi/bugreport.cgi?bug=30629#112>.
* gnu/system/linux-initrd.scm (default-initrd-modules): Add virtio
modules.
(base-initrd): Remove #:virtio? and 'virtio-modules'.
* gnu/system/vm.scm (expression->derivation-in-linux-vm)
(system-qemu-image, virtualized-operating-system): Remove uses of
#:virtio?.
* doc/guix.texi (Initial RAM Disk): Update 'base-initrd' doc.
eac026e5c8