[MachineOutliner][NFC] Use flags set in all candidates to check for calls

If we keep track of if the ContainsCalls bit is set in the MBB flags for each
candidate, then we have a better chance of not checking the candidate for calls
at all.

This saves quite a few checks in some CTMark tests (~200 in Bullet, for
example.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@346816 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed