Bug fix in module_chem_utilities.F

[saneku]

Removed unnecessary factor in computation of dry air density in module_chem_utilities.F

TYPE: bug fix

KEYWORDS: WRF-Chem, dry air density

SOURCE: NOAA GSL, Alexander Ukhov (KAUST)

DESCRIPTION OF CHANGES:
Problem:
It was found that dry air density was miscalculated.

Solution:
Removed unnecessary factor. Simulations before and after did not show any significant difference, as expected.

LIST OF MODIFIED FILES:
M chem/module_chem_utilities.F

TESTS CONDUCTED:

1. Do mods fix problem? How can that be demonstrated, and was that test conducted?
2. Are the Jenkins tests all passing?

RELEASE NOTE: Fixed calculation of dry air density in module_chem_utilities.F. The bug had a very minor effect.

[weiwangncar]

The regression test results:

Test Type              | Expected  | Received |  Failed
= = = = = = = = = = = = = = = = = = = = = = = =  = = = =
Number of Tests        : 23           24
Number of Builds       : 60           57
Number of Simulations  : 158           150        0
Number of Comparisons  : 95           86        0

Failed Simulations are: 
None
Which comparisons are not bit-for-bit: 
None