Merge branch 'ambrad/homme/flush-homme-log-1' (PR #6646)

Homme(xx): Flush the log before calling MPI_Abort in Homme's abortmp.

This is an attempt to assure atm.log (EAM) and homme_atm.log (EAMxx) get full
output when the dycore calls MPI_Abort.

[BFB]

components/homme/src/share/parallel_mod.F90

@@ -274,6 +274,7 @@ subroutine abortmp(string)
 #endif
 #endif
     character*(*) string
+    call flush(iulog)
 #ifdef CAM
     call endrun(string)
 #else