Adding timeout to verify_metadata method in test_server_basicops

Sometimes the test_server_basicops test may fail with the following
traceback http://paste.openstack.org/show/412497/. The reason of this
failure is that the floating IP doesn't appear in
http://169.254.169.254/latest/meta-data/public-ipv4 immediately and
we should check metadata within some timeout, not only once.

Closes-Bug: #1483585

Change-Id: I2f3d5d153cc67fefe048c80304d5477072660e7b
1 file changed