library: Fix memory leak in procps_users

Need to free the sesions_list after using it, this was
introduced by me when checking the session class.

Thanks to Thorsten Kukuk from SUSE (All capitals)
for catching this and the patch.

References:
 commit 734930e476
 https://www.freelists.org/post/procps/New-procps-release-soon,10

Signed-off-by: Craig Small <csmall@dropbear.xyz>

library/uptime.c

@@ -91,6 +91,9 @@ PROCPS_EXPORT int procps_users(void)
                     numuser++;
                 free(class);
             }
+	    for (i = 0; i < sessions; i++)
+	      free(sessions_list[i]);
+	    free(sessions_list);
             return numuser;
         }
     }