Revert "hhvm: remove jemalloc profiling config due to a bug in HHVM"

I confirmed that there is no bug. I simply had a spurious /etc/malloc.conf on mw1114.

This reverts commit af0def74bb63f3389e5ff1c83e185e0becafa512.

Change-Id: I9897819edc6b55d959af5f35a70cb83333498389