Update phi nodes in LowerTypeTests control flow simplification

D33925 added a control flow simplification for -O2 --lto-O0 builds that
manually splits blocks and reassigns conditional branches but does not
correctly update phi nodes. If the else case being branched to had
incoming phi nodes the control-flow simplification would leave phi nodes
in that BB with an unhandled predecessor.

Patch by Vlad Tsyrklevich!

Differential Revision: https://reviews.llvm.org/D36012

llvm-svn: 309621