Bug fix for amrex::Subtract when called with interger nghost (#3634)

## Summary
`amrex::Subtract` leads to an infinite recursion when invoked with an
integer value for nghost. To address this issue, explicit casting of the
integer to `IntVect` has been incorporated.

## Checklist

The proposed changes:
- [x] fix a bug or incorrect behavior in AMReX
- [ ] add new capabilities to AMReX
- [ ] changes answers in the test suite to more than roundoff level
- [ ] are likely to significantly affect the results of downstream AMReX
users
- [ ] include documentation in the code and/or rst files, if appropriate

Src/Base/AMReX_FabArrayUtility.H

@@ -1103,7 +1103,7 @@ template <class FAB,
 void
 Subtract (FabArray<FAB>& dst, FabArray<FAB> const& src, int srccomp, int dstcomp, int numcomp, int nghost)
 {
-    Subtract(dst,src,srccomp,dstcomp,numcomp,nghost);
+    Subtract(dst,src,srccomp,dstcomp,numcomp,IntVect(nghost));
 }
 
 template <class FAB,