Fix callout_init_rm() in the shared case, allocating storage for 'struct rm_priotracker' directly in the softclock thread. Now consumers can pass CALLOUT_SHAREDLOCK flag to callout initialization routine safely. The choice of the already existing flags  instead of special casing shared rmlocks is done to prevent consumer footshooting.
Fix callout_init_rm() in the shared case, allocating storage for 'struct
rm_priotracker' directly in the softclock thread. Now consumers can
pass CALLOUT_SHAREDLOCK flag to callout initialization routine safely.
The choice of the already existing flags  instead of special casing
shared rmlocks is done to prevent consumer footshooting.

Suggested by:	jhb
Reviewed by:	jhb
Approved by:	re (delphij)

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase