Bug #34833609 Assertion failure: btr0load.cc:1489:rec_count <= n_recs thread 140094285530880

There is an off-by-one error with respect to rec_count and i variable in
the Page_load::copy_to() function. And set the REC_INFO_MIN_REC_FLAG in the
newly added root page in Btree_load::Merger::root_split().

Change-Id: I4f6a2e79541963009aded15aafd225c67b2fcb40

Author: gurusami