The output parameter `role_arr` of semanage_user_get_roles() is an array
of non-owned role names. Since the array is never used again, as its
contents have been copied into the return value `roles`, free it.
Example leak report from useradd(8):
Direct leak of 8 byte(s) in 1 object(s) allocated from:
#0 0x5597624284a8 in __interceptor_calloc (./shadow/src/useradd+0xee4a8)
#1 0x7f53aefcbbf9 in sepol_user_get_roles src/user_record.c:270:21
3be312e0cf