Exclude Docker Volumes from Storage Check (#6)

* exclude docker volumes

* added missing import

* Update check_synology.py

* Update check_synology.py

* additional filter

possible volume names are 
/volume'X'/@docker/id/'something'/
and
/volume'X'/@docker <- this needs another regex check

alternative : 
look for "/volume.+/@DocKe.+"

Might lead to false positives?

* updated to wernerfred recommendations

check_synology.py

@@ -2,6 +2,7 @@
 import argparse
 import sys
 import math
+import re
 
 AUTHOR = "Frederic Werner"
 VERSION = 0.1
@@ -123,7 +124,7 @@ def exitCode():
     perfdata = '|'
     for i in range(1,256,1):
         storage_name = snmpget('1.3.6.1.2.1.25.2.3.1.3.' + str(i))
-        if storage_name.startswith("/volume"):
+        if re.match("/volume(?!.+/@docker.*)", storage_name) :
             allocation_units = snmpget('1.3.6.1.2.1.25.2.3.1.4.' + str(i))
             size = snmpget('1.3.6.1.2.1.25.2.3.1.5.' + str(i))
             used = snmpget('1.3.6.1.2.1.25.2.3.1.6.' + str(i))