dnsdist-1.5.x: Fix building with LLVM11

[rgacogne]

Short description

Backport of #9408 to dnsdist-1.5.x.

There's a typo on line 529, where it says "true", but the double quotes cause a type cast error on LLVM11.

dnsdist-console.cc:529:32: error: type 'const char [5]' cannot be narrowed to 'bool' in initializer list [-Wc++11-narrowing]
  { "SetNegativeAndSOAAction", "true", "nxd, zone, ttl, mname, rname, serial, refresh, retry, expire, minimum [, options]", "Turn a query into a NXDomain or NoData answer and sets a SOA record in the additional section" },
                               ^~~~~~
dnsdist-console.cc:529:32: note: insert an explicit cast to silence this issue
  { "SetNegativeAndSOAAction", "true", "nxd, zone, ttl, mname, rname, serial, refresh, retry, expire, minimum [, options]", "Turn a query into a NXDomain or NoData answer and sets a SOA record in the additional section" },
                               ^~~~~~
                               static_cast<bool>( )
1 error generated.

(cherry picked from commit e7c6996)

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• checked that this code was merged to master