MB-33933: Disable MagmaKVStoreTest.Sanity under UBSan

Currently fails ~50% of the time under UBSan:

    null pointer passed as argument 2, which is declared to never be null
    #0 0x7fc16960c806 in magma::Buffer::CopyInto(char const*, unsigned long) magma/util/buffer.cc:194
    #1 0x7fc1692b5727 in magma::WAL::AddRecord(magma::WAL::walRecType, std::vector<magma::Slice*, std::allocator<magma::Slice*> > const&, magma::WALOffset&) magma/wal/wal.cc:281
    #2 0x7fc1692b89a2 in magma::WAL::endTxn(magma::WAL::walRecType, magma::Slice&) magma/wal/wal.cc:206
    #3 0x7fc1692b95ab in magma::WAL::AbortTxn() magma/wal/wal.cc:233
    #4 0x7fc16958941e in magma::Magma::Impl::recovery() magma/magma/recovery.cc:356
    #5 0x7fc1695cf467 in magma::Magma::Open() magma/magma/magma.cc:143
    #6 0x2e7a2f3 in MagmaKVStore::MagmaKVStore(MagmaKVStoreConfig&) kv_engine/engines/ep/src/magma-kvstore/magma-kvstore.cc:445
    #7 0x29c9679 in std::_MakeUniq<MagmaKVStore>::__single_object std::make_unique<MagmaKVStore, MagmaKVStoreConfig&>(MagmaKVStoreConfig&) /usr/local/include/c++/7.3.0/bits/unique_ptr.h:825
    #8 0x29c9679 in KVStoreFactory::create(KVStoreConfig&) kv_engine/engines/ep/src/kvstore.cc:97
    #9 0x1cb0232 in setup_kv_store kv_engine/engines/ep/tests/module_tests/kvstore_test.cc:193
    #10 0x1e572f7 in MagmaKVStoreTest::SetUp() kv_engine/engines/ep/tests/module_tests/kvstore_test.cc:2605

Change-Id: I02cd0a0d71e728296ab9a6027b06d17809fc3248
Reviewed-on: http://review.couchbase.org/108269
Reviewed-by: Paolo Cocchi <paolo.cocchi@couchbase.com>
Tested-by: Build Bot <build@couchbase.com>

Author: daverigby

engines/ep/tests/module_tests/kvstore_test.cc

@@ -2615,6 +2615,12 @@ class MagmaKVStoreTest : public KVStoreTest {
 };
 
 // Simple sanity test to verify magma
+#if !defined(UNDEFINED_SANITIZER)
+// MB-33933: Currently broken under UBSan:
+//     magma/util/buffer.cc:194:11: runtime error: null pointer passed as
+//     argument 2, which is declared to never be null
 TEST_F(MagmaKVStoreTest, Sanity) {
 }
-#endif
+#endif // UNDEFINED_SANITIZER
+
+#endif // EP_USE_MAGMA