Updated tools version to 2.0.0

Also merged lint-style (gofmt) into golangci-lint (enabled gofmt).
Also removed redundant lint-sanity (govet) which is already checked by golangci-lint.
Also made minor code changes to pass new golangci-lint tests.
Also changed lint-mod slightly so it reverts any changes it makes go.mod, go.sum, and vendor/.

VOL-2647

Change-Id: I2919e65ae29e01c81d1bf7ef113c3189e8227939
diff --git a/.golangci.yml b/.golangci.yml
index b2db7aa..da0158b 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -13,4 +13,13 @@
 # limitations under the License.
 
 run:
-  modules-download-mode: vendor
\ No newline at end of file
+  modules-download-mode: vendor
+
+linters:
+  enable:
+    #- gochecknoglobals
+    #- gochecknoinits
+    #- gocritic
+    - gofmt
+    #- golint
+    #- unparam