Make will_runs look past all_node reservations

Bug 3007

e.g.
brian@lappy:~/slurm/master/lappy$ scontrol show res
ReservationName=root_167 StartTime=2016-10-12T10:24:35 EndTime=2016-10-12T10:54:35 Duration=00:30:00
   Nodes=lappy[1-10] NodeCnt=10 CoreCnt=40 Features=(null) PartitionName=(null) Flags=OVERLAP,SPEC_NODES,ALL_NODES
   TRES=cpu=80
   Users=root Accounts=(null) Licenses=(null) State=ACTIVE BurstBuffer=(null) Watts=n/a

ReservationName=root_168 StartTime=2016-10-12T10:24:37 EndTime=2016-10-12T11:24:37 Duration=01:00:00
   Nodes=lappy[1-10] NodeCnt=10 CoreCnt=40 Features=(null) PartitionName=(null) Flags=OVERLAP,SPEC_NODES,ALL_NODES
   TRES=cpu=80
   Users=root Accounts=(null) Licenses=(null) State=ACTIVE BurstBuffer=(null) Watts=n/a

brian@lappy:~/slurm/master/lappy$ sbatch --wrap="sleep 60" -t1 --test-only
sbatch: Job 14435 to start at 2016-10-12T11:24:37 using 1 processors on lappy1