do not use sh-style quoting for kernel options

Although Anaconda parses /proc/cmdline using shlex.split, the kernel
itself defines its command line in bootparam(7) as space-separated
tokens with no quoting or escaping. Dracut follows this lead and
parses /proc/cmdline as space-separated tokens with no quoting.

In practice no kernel options ever need to contain spaces or shell
metachars so there is no effective difference. The one corner case we
know of is URLs containing the tilde character, which pipes.quote
considers to need quoting.

Bug: 1067924
Change-Id: Idffc82bc4b4a4a0166418e8343738ce0581667f9