[#2207] Removed unnecessary null check

STACK Output:
bug: anti-dce
model: |
  %tobool = icmp ne %class.osauth_auth_plugin* %7, null, !dbg !1630
  -->  true
  ************************************************************
  if.then:
  call void (i32, i8*, ...)* @rodsLog(i32 3, i8* getelementptr inbounds ([52 x i8]* @.str60, i32 0, i32 0)), !dbg !1632
  br label %return, !dbg !1634
stack:
  - /home/kellerb/software/root-stack/irods/plugins/auth/osauth/libosauth.cpp:709:0
ncore: 1
core:
  - /home/kellerb/software/root-stack/irods/plugins/auth/osauth/libosauth.cpp:690:0
    - null pointer dereference