DTRT with target names

If an iSCSI target name is a short name, then it should get appended
to the global config base name.  However if it is a full iqn
then ignore the global base name and just use the target name.

Example:

Base name: iqn.2002.05.org.example.ctl

Target name: test

Generated target name should be: iqn.2002.05.org.example.ctl:test

Target name: iqn.2014.05.gov.whitehouse:secrettarget

Generated target name should be: iqn.2014.05.gov.whitehouse:secrettarget

Before this fix the generated target name in the second case would have been:

iqn.2002.05.org.example.ctl:iqn.2014.05.gov.whitehouse:secrettarget

(cherry picked from commit bf916e6ba0df408a5c5b8fac1af6b94d6b1c39e1)