Group conditional logic to clarify precedence

It may not be clear to the developer that `&&` takes precedence over `||`. This change was recommended by a code quality scan.

src/main/edu/wisc/doit/uwphps/preauth/FederatedPreauthUserDetailsProvider.php

@@ -27,8 +27,8 @@ class FederatedPreauthUserDetailsProvider extends UserDetailsProvider
     public function loadUser()
     {
         // Return null if no Shib session is found
-        if ($this->httpHeaders && !getenv(static::SHIB_SESSION_ID_HTTP) ||
-            !$this->httpHeaders && !getenv(static::SHIB_SESSION_ID)) {
+        if (($this->httpHeaders && !getenv(static::SHIB_SESSION_ID_HTTP)) ||
+            (!$this->httpHeaders && !getenv(static::SHIB_SESSION_ID))) {
             return null;
         }
 

src/main/edu/wisc/doit/uwphps/preauth/PreauthUserDetailsProvider.php

@@ -29,8 +29,8 @@ class PreauthUserDetailsProvider extends UserDetailsProvider
     public function loadUser()
     {
         // Return null if no Shib session is found
-        if ($this->httpHeaders && !getenv(static::SHIB_SESSION_ID_HTTP) ||
-            !$this->httpHeaders && !getenv(static::SHIB_SESSION_ID)) {
+        if (($this->httpHeaders && !getenv(static::SHIB_SESSION_ID_HTTP)) ||
+            (!$this->httpHeaders && !getenv(static::SHIB_SESSION_ID))) {
             return null;
         }