Fix convert dtype when writing numpy array from h5dataset (#427)

Co-authored-by: Andrew Tritt <ajtritt@lbl.gov>

src/hdmf/build/objectmapper.py

@@ -130,7 +130,7 @@ def __resolve_numeric_dtype(cls, given, specified):
         """
         g = np.dtype(given)
         s = np.dtype(specified)
-        if g is s:
+        if g == s:
             return s.type, None
         if g.itemsize <= s.itemsize:  # given type has precision < precision of specified type
             # note: this allows float32 -> int32, bool -> int8, int16 -> uint16 which may involve buffer overflows,