ceph_io: add test

docs/20_Checks/check_ceph_io.md

@@ -11,12 +11,11 @@ It returns a single line for the status and performance data.
 
 ## Syntax
 
-```
-$ check_ceph_io --help
+```txt
 ______________________________________________________________________
 
 CHECK_CEPH_IO 
-v1.0
+v1.2
 
 (c) Institute for Medical Education - University of Bern
 Licence: GNU GPL 3
@@ -30,6 +29,19 @@ check_ceph_io
 
 OPTIONS:
     -h or --help   show this help.
+    -t [STRING]    test a value; for debugging purposes
+                   Without a string internally stored values will be tested
+
+EXAMPLE:
+check_ceph_io
+    no parameters; normal usage to get the ceph io data
+
+check_ceph_io -t
+    Run a few builtin tests
+
+check_ceph_io -t "   client: 255 B/s rd, 0 op/s rd, 0 op/s wr"
+    Test a given string
+
 ```
 
 ### Parameters