Revert setting auxiliary processes as Gp_role GP_ROLE_UTILITY

Setting auxiliary processes as GP_ROLE_UTILITY actually works fine
until a standby master is initialized and started.  The standby master
can go into certain redo paths such as redoDistributedCommitRecord
which will exit early if the Gp_role is GP_ROLE_UTILITY.  Having the
Gp_role check in these redo paths is not correct and will be revisited
for refactor some other day.

Commit context:
https://github.com/greenplum-db/gpdb/commit/6810843fe1c2565dd4f6225ca2838c182b03ca72

src/backend/storage/lmgr/proc.c

@@ -495,12 +495,6 @@ InitAuxiliaryProcess(void)
 	int			proctype;
 	int			i;
 
-	/*
-	 * Set Gp_role to GP_ROLE_UTILITY to avoid auxiliary process from going
-	 * into any GP_ROLE_DISPATCH code paths if any exists.
-	 */
-	Gp_role = GP_ROLE_UTILITY;
-
 	/*
 	 * ProcGlobal should be set up already (if we are a backend, we inherit
 	 * this by fork() or EXEC_BACKEND mechanism from the postmaster).