[MemorySSA] Don't use template when the clone is a simplified instruction.
LoopRotate doesn't create a faithful clone of an instruction, it may
simplify it beforehand. Hence the clone of an instruction that has a
MemoryDef associated may not be a definition, but a use or not a memory
Don't rely on the template when the clone may be simplified.
Subscribers: jlebar, Prazek, llvm-commits
Differential Revision: https://reviews.llvm.org/D63355