M_NOWAIT can only be used in a driver where a failed memory allocation is

M_NOWAIT can only be used in a driver where a failed memory allocation is
recoverable, such as in a network driver.  FreeBSD seems to have a looser
definition but in DragonFly M_NOWAIT really means M_NOWAIT ... any blocking
at all, including waiting on the BGL or getting the kernel_map lock,
will result in a failure NULL.

Change all M_NOWAIT's to either M_WAITOK or M_INTWAIT.