Increase timeout for decomission operation

Recently we saw a number of integration tests failure due to timeout
during nodes decommision. Right now it is 30 seconds. There is no
reason to keep it that low, and increasing it to 5 minutes should
help avoid false failures on CI.

Change-Id: Ibaba8a55879a95255beae260647022777938c38f
Merge "Increase timeout for decomission operation"