tests: Fix flaky kola destructive tests

tests: Fix flaky kola destructive tests

The kargs-proc-cmdline-quoted test was parsing `ostree admin status`
text output with a sed regex that assumes the line ends with the
deployment serial.  Status annotations like "(pending)" break this;
just reuse $host_commit from libinsttest.sh instead.

For soft-reboot, make the initramfs regeneration check non-fatal
since dracut can fail inside bwrap in CI VMs.  The kargs-based
kernel state check still covers the same rejection path.