switch/nrt: correct some logic if NULL pointer

The test for NRT_NULL_MAGIC failed to capture some problems
if the pointer to the structure was NULL. This is an ammendment
to commit 2a55aa0b1bf5d9a2ff3cd350eae69c29122407bf
Fix potential memory leak.
Add comment for bug #632.
Job array dependency performance improvement

Cache results for major performance improvement.
bug 636
Merge branch 'slurm-2.6'

Conflicts:
	src/plugins/switch/nrt/nrt.c
change logging for step create on suspended job

If a job is suspended, log the step create failure using debug
rather than info in slurmctld
Fix sleep on step create for suspended job

Rather than continuously retrying a step create for suspended jobs,
add a sleep with exponential backoff
Merge branch 'slurm-2.6'
job_submit/lua - initialize user msg to NULL

Without this, an xfree could be called for an arbitrary memory location
Change SLURM -> Slurm
Missed one
Remove whitespace
Merge remote-tracking branch 'origin/slurm-2.6'

Conflicts:
	RELEASE_NOTES
Add missing options to the print of TaskPluginParam.
Merge remote-tracking branch 'origin/slurm-2.6'
Add a new environment variable PMI2_CONNECT_TO_SERVER. If set in the MPI
application environment the PMI2 library will connect the the PMI2
server (slurmstepd) instead of using the provided PMI_FD socket.
CRAY - Fix issue where multi-prog is used but doesn't have any arguments
on any of the commands.
Correct code generating compiler warning.
Minor typo fix
Add missing xstr alias'