[testsuite] Drop characters that can't be decoded, restoring parity with Py2.
[testsuite] Drop characters that can't be decoded, restoring parity with Py2.

Tests that check the output of `memory find` may trip over
unreadable characters, and in Python 3 this is an error.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@355612 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb