Upgrade blevesearch to v0.8.1 (#9177)

For #1441

https://github.com/blevesearch/bleve/commit/a91b427b59b893f112021841ba7370d285f8426f

vendor/github.com/blevesearch/bleve/.travis.yml

@@ -3,9 +3,9 @@ sudo: false
 language: go
 
 go:
- - "1.9.x"
  - "1.10.x"
  - "1.11.x"
+ - "1.12.x"
 
 script:
   - go get golang.org/x/tools/cmd/cover
@@ -15,7 +15,12 @@ script:
   - gvt restore
   - go test -race -v $(go list ./... | grep -v vendor/)
   - go vet $(go list ./... | grep -v vendor/)
-  - errcheck -ignorepkg fmt $(go list ./... | grep -v vendor/)
+  - go test ./test -v -indexType scorch
+  - if [[ ${TRAVIS_GO_VERSION} =~ ^1\.10 ]]; then
+        echo "errcheck skipped for go version" $TRAVIS_GO_VERSION;
+    else
+        errcheck -ignorepkg fmt $(go list ./... | grep -v vendor/);
+    fi
   - docs/project-code-coverage.sh
   - docs/build_children.sh