VMware: cinder-volume create_session fail at retry

cinder-volume exits with an exception while accessing a None
object during retry of create session failure.

Closes-Bug: #1374585

Change-Id: I1d8dd034e9c6eb7568cf6f243a203df7de1777da
Adds openSUSE support for developer documentation

Add information for openSUSE as developer platform.

Change-Id: I3d5429f78b06cd38b10756570acea96fb23ed021
Fix race condition in ISCSIConnector disconnect_volume

The list of devices returned by driver.get_all_block_devices() will
sometimes contain broken symlinks as the SCSI device has been deleted
but the udev rule for the symlink has not yet completed.

Adding in a check to os.path.exists() will ensure that we will not
consider the broken symlinks as an “in use” device.

Change-Id: Ibb869e10976f894f9e18e9edec6739c2c3bea68c
Closes-Bug: #1375382
Merge "Adds openSUSE support for developer documentation"
Merge "Fix race condition in ISCSIConnector disconnect_volume"
Merge "VMware: cinder-volume create_session fail at retry"