Updating atmospheric_physics submodule. (#318)

Tag name (required for release branches):
Originator(s): @mwaxmonsky

Description (include the issue title, and the keyword ['closes',
'fixes', 'resolves'] followed by the issue number): Updates
atmospheric_physics submodule to enable vertical diffusion solver
accessible from submodule.

Describe any changes made to build system: N/A

Describe any changes made to the namelist: N/A

List any changes to the defaults for the input datasets (e.g. boundary
datasets): N/A

List all files eliminated and why: None

List all files added and what they do: None

List all existing files that have been modified, and describe the
changes:
(Helpful git command: `git diff --name-status
development...<your_branch_name>`)
M       .gitmodules
M       src/physics/ncar_ccpp
- Updates submodule and its directory to latest tagged release to make
vertical diffusion solver available directly in SIMA.

If there are new failures (compared to the
`test/existing-test-failures.txt` file),
have them OK'd by the gatekeeper, note them here, and add them to the
file.
If there are baseline differences, include the test and the reason for
the
diff. What is the nature of the change? Roundoff?

derecho/intel/aux_sima: All PASS

derecho/gnu/aux_sima: All PASS

If this changes climate describe any run(s) done to evaluate the new
climate in enough detail that it(they) could be reproduced: N/A

CAM-SIMA date used for the baseline comparison tests if different than
latest: N/A

.gitmodules

@@ -20,7 +20,7 @@
 [submodule "ncar-physics"]
         path          = src/physics/ncar_ccpp
 	url           = https://github.com/ESCOMP/atmospheric_physics
-	fxtag         = e95c172d7a5a0ebf054f420b08416228e211baa3
+	fxtag         = atmos_phys0_06_000
         fxrequired    = AlwaysRequired
         fxDONOTUSEurl = https://github.com/ESCOMP/atmospheric_physics
 [submodule "ccs_config"]