If the target symbolic link already existed, an invalid link in target
was created to java/target. Fixed by checking if the link exists before
creating it
Change-Id: Ie53f396820e0e0022a949799b2b433b5ae11c4d1
Also, pull and build monasca-common directly instead of using
jars from tarballs.openstack.org since zuul often gets backed
up and jars don't get updated fast enough
Change-Id: I22fc5cfc085a583c337fca199d5e49ead93fcbb7