Add support for special char in volume metadata

Using special characters such as "&" in volume metadata caused SAX
parser to split text into multiple child nodes, as stated in the
specs for SAX parsers. In this case extract_text would return
'None' because text was return if there was exactly
one child node. Concatenating the values of child nodes accounts
for SAX parsers splitting contigous characters into
multiple chunks.

Change-Id: I3709789d33ff7b07eaeaf725f5183105443d0abc
Closes-Bug: #1268513
Remove a catching exception during delete_volume

GlanceMetadataNotFound Exception was catching during
a call to volume_glance_metadata_delete_by_volume().
This exception is never thrown by the implementation.
This catching has been removed.

Change-Id: Ifa15df5d9c4517f75a1a050ff5aa34225f33931b
Closes-Bug: #1274601
Merge "Remove a catching exception during delete_volume"
Merge "Add support for special char in volume metadata"