Enable readability-implicit-bool-conversion checks

These checks ensure that we're not implicitly converting ints or
pointers into bools, which makes the code easier to read.

Tested:
Ran series through redfish service validator.  No changes observed.
UUID failing in Qemu both before and after.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I1ca0be980d136bd4e5474341f4fd62f2f6bbdbae
diff --git a/include/http_utility.hpp b/include/http_utility.hpp
index 740e218..3970992 100644
--- a/include/http_utility.hpp
+++ b/include/http_utility.hpp
@@ -53,7 +53,7 @@
     for (const char c : value)
     {
         // Keep alphanumeric and other accepted characters intact
-        if (isalnum(c) || c == '-' || c == '_' || c == '.' || c == '~')
+        if ((isalnum(c) != 0) || c == '-' || c == '_' || c == '.' || c == '~')
         {
             escaped << c;
             continue;