Silence exceptions from qpid connection.close() (from oslo)

This is commit 15d8d698b7 in oslo-incubator.

Fixes bug 1185465

Don't log exceptions that happen during connection.close().  They're
not surprising (a closed socket can't be read or written), don't
require sysadmin attention, and provide red herrings in the logs
to distract from finding real root causes of problems.

Change-Id: Ia0e25fbc11094b5ad5d6d2cf7d0e786acb3df1f6
Merge "Silence exceptions from qpid connection.close() (from oslo)"