Fix for possible memory corruption in srun when running heterogeneous
job steps.
bug 4626

This should never happen in practice
Coverity CID 181927

Coverity CID 181959

Coverity CID 181960

This partially reverts 89bcd975 and aac6bd39

Turns out you can't use a list_for_each and lock something inside the
list_for_each function that does a lock without the write lock.

Bug 4611

This reverts commit ff3e77f4.

This partially reverts 89bcd975 and aac6bd39

Turns out you can't use a list_for_each and lock something inside the
list_for_each function that does a lock without the write lock.

Bug 4611

Otherwise undocumented, and does not do anything.
Will be removed in 18.08.

This should never happen with a valid feature specificiaton
Coverity CID 181927

This should not happen with a valid feature expression, but this
  change hardens the code
Coverity CID 181926

Coverity CID 181925

Coverity CID 181924

in the current directory but not in the --chdir specified cwd.

Now srun looks for the command in specified cwd and differentiates all
the possible cases where a command starts with ./ (relative), with /
(absolute), and with a different char indicating a command that is in
the path.

Fix also for a PATH variable starting by '.', now it is relative to
specified cwd.

bug 4392

Fix job array dependency with "aftercorr" option and some task arrays in
    the first job fail. This fix lets all task array elements that can run
    proceed rather than stopping all subsequent task array elements.
Bug 4590

Creating a copy of the actual environment in env->env defines a new pointer,
then next call to setup_env and setenvf doesn't define variables in the global
environment but in this new copy.

Bug 4615

This fixes the problem introduced in by commit
777a45f9 and maintains proper PMIx
operation.
bugs 4132 and 4615

 -- node_features plugin - Add suport for XOR & XAND of job constraints (node
    feature specifications).
 -- Add support for parenthesis in a job's constraint specification to group
    like options together. For example
    --constraint="[(knl&snc4&flat)*4&haswell*1]" might be used to specify that
    four nodes with the features "knl", "snc4" and "flat" plus one node with
    the feature "haswell" are required.

node_feature/knl_cray - Fix memory leak that can occur during normal
    operation. This will happen when an update request for a specific
    node happens.

If CnselectPath and/or SyscfgPath defined in knl_cray.conf file and
  slurmctld reconfigured, the original values of those paraemters
  would be over-written and their memory leaked.

Use FREE_NULL_BUFFER instead, otherwise we could attempt to
free_buffer a second time if we jump to the rwfail label.

bug4491

to preempt other eligible jobs.

Bug 4279

Missing from 390da8cf

Bug 4595

slurmdb_pack_assoc_usage() will assert with a NULL usage ptr.

7d9a75df uncovered that slurmdb_pack_assoc_usage() expects a usage
ptr.

Used by new node features development