Change M_NOWAIT to M_WAITOK. This does not fix any known issues but it

Change M_NOWAIT to M_WAITOK.  This does not fix any known issues but it
makes the code properly conform to the malloc API.  Using M_NOWAIT
during booting to mean 'if we block here we would deadlock during boot' but
then assuming that the return value is always non-NULL is worse then
using M_WAITOK and potentially allowing the system to deadlock but, not
really, because there is plenty of memory available during booting.