Fix dump delete all command defect

"openbmctool.py dump delete all" command can't work due to some entries
do not have valid entry number. Add the checking for the valid entry
number.

Tested: Test dump list, dump delete -n <num>, dump delete all and
        dump retrieve <num>

Change-Id: If1192631ec204df14cf46bed2278696a4911be8e
Signed-off-by: Alvin Wang <alvinwang@msn.com>
diff --git a/thalerj/openbmctool.py b/thalerj/openbmctool.py
index f93c7c2..4541404 100755
--- a/thalerj/openbmctool.py
+++ b/thalerj/openbmctool.py
@@ -1422,8 +1422,9 @@
     d = vars(args)
     dumpNums = []
     for dump in dumpList:
-        if '/xyz/openbmc_project/dump/internal/manager' not in dump:
-            dumpNums.append(int(dump.strip().split('/')[-1]))
+        dumpNum = dump.strip().split('/')[-1]
+        if dumpNum.isdigit():
+            dumpNums.append(int(dumpNum))
     d['dumpNum'] = dumpNums
 
     return bmcDumpDelete(host, args, session)