Issue title: Intermittent timeouts in OpenMP unit tests on KNL testbed Bowman
 Issue body: In gcc/6.1 and gcc/7.1 OpenMP builds on Bowman the `KokkosCore_UnitTest_OpenMP` is intermittently timing out.

Scanning over the times of the component tests in the [timeout](https://jenkins-son.sandia.gov/job/Kokkos_SLURM_inner_test/36086/console) vs [passing](https://jenkins-son.sandia.gov/job/Kokkos_SLURM_inner_test/36046/consoleFull) cases a couple observations are worth noting:

1. Nearly 3X discrepancy in the `team_scan` test, I'm not sure if this degree of fluctuation is to be expected on KNL, poor affinity setting, or a sign of some underlying issue

test | passing case | timeout case
--- | --- | ---
openmp.team_scan | 41618 ms | 118193 ms

2. The total test time in passing cases is very near the timeout threshold - should the timeout be increased from 1500 s, or should problem sizes in the tests be reduced?

test | passing case | timeout case
--- | --- | ---
KokkosCore_UnitTest_OpenMP | 1451.48 sec | Timeout 1500.30 sec

Aside from the inconsistent `team_scan` test time, the two tests consistently taking the longest are:

`openmp.team_long_reduce (582533 ms)`
`openmp.team_double_reduce (582214 ms)`

I'll mark as a question for now with the 3.1 milestone, others can relabel as appropriate. Adding @crtrott 

Sample reproducer instructions:
```
module load gcc/7.1.0 hwloc/1.11.3

export OMP_PROC_BIND=spread
export OMP_PLACES=threads
source ../scripts/testing_scripts/update_lib.sh bowman
$KOKKOS_PATH/generate_makefile.bash \
    --arch=KNL \
    --cxxflags="-Wall -Wshadow -pedantic -Werror -Wsign-compare -Wtype-limits -Wignored-qualifiers -Wempty-body -Wclobbered -Wuninitialized" \
    --with-hwloc=$HWLOC_ROOT \
    --compiler=g++ \
    --with-devices=OpenMP,Serial
```

 Comments: 
 Comment 0: Discussed briefly during the meeting, will add option to increase timeout and update for these tests
 Comment 1: Adjusted timeout in the nightly tests, closing.
{'source': 'GithubIssues', 'repo_name_with_owner': 'kokkos/kokkos', 'issue_id': 587867319, 'repo_stars': 1134.0}