utils: rm_offset_get_from_fd: Break early if not contiguous

Completing the current loop iteration if the current extent is not
contiguous with the last means the extent flags and file offset are
updated as if the extents *were* contiguous. In general, this causes
calling code to skip every second extent!

Also remove a redundant write to file_offset_next that is always
clobbered after the loop exits.

Fixes sahib#527

lib/utilities.c

@@ -1229,15 +1229,11 @@ RmOff rm_offset_get_from_fd(int fd, RmOff file_offset, RmOff *file_offset_next,
                 /* check if subsequent extents are contiguous */
                 if(fm_ext.fe_physical != expected) {
                     /* current extent is not contiguous with previous, so we can stop */
-                    done = TRUE;
+                    g_free(fm);
+                    break;
                 }
             }
 
-            if(!done && file_offset_next != NULL) {
-                /* update logical offset of next fragment */
-                *file_offset_next = fm_ext.fe_logical + fm_ext.fe_length;
-            }
-
             if(fm_ext.fe_flags & FIEMAP_EXTENT_DATA_INLINE) {
                 rm_util_set_nullable_bool(is_inline, TRUE);
             }