Replace `false` with `exit 1`

Some scripts contained `false` for returning 1 to callers instead of
`exit 1` and that works like:

  $ false
  $ echo $?
  1
  $

But that made confusion in a PR review process.
So this replaces `false` with `exit 1` for long-term maintenance.

hack/verify-golint.sh

@@ -94,7 +94,7 @@ else
     echo 'checking by adding it to hack/.golint_failures (if your reviewer is okay with it).'
     echo
   } >&2
-  false
+  exit 1
 fi
 
 if [[ ${#not_failing[@]} -gt 0 ]]; then
@@ -106,7 +106,7 @@ if [[ ${#not_failing[@]} -gt 0 ]]; then
     done
     echo
   } >&2
-  false
+  exit 1
 fi
 
 if [[ ${#gone[@]} -gt 0 ]]; then
@@ -118,5 +118,5 @@ if [[ ${#gone[@]} -gt 0 ]]; then
     done
     echo
   } >&2
-  false
+  exit 1
 fi

hack/verify-shellcheck.sh

@@ -169,7 +169,7 @@ else
     echo 'checking by adding it to hack/.shellcheck_failures (if your reviewer is okay with it).'
     echo
   } >&2
-  false
+  exit 1
 fi
 
 if [[ ${#not_failing[@]} -gt 0 ]]; then
@@ -181,7 +181,7 @@ if [[ ${#not_failing[@]} -gt 0 ]]; then
     done
     echo
   } >&2
-  false
+  exit 1
 fi
 
 # Check that all failing_packages actually still exist
@@ -199,5 +199,5 @@ if [[ ${#gone[@]} -gt 0 ]]; then
     done
     echo
   } >&2
-  false
+  exit 1
 fi