jobs/coverity: don't cd ~/osmo-ci/coverity

Run the coverity/jenkins.sh from the osmo-ci.git repository that jenkins
checks out at the beginning of the build, instead of using a copy in ~/
that is updated whenever pushing to master. This makes it less
confusing, I configured the job to use a WIP branch and didn't realize
that it still used the code from master.

Change-Id: Ie992d71d2afec6982447b8fe3626c821a9e48d19

coverity/jenkins.sh

@@ -3,8 +3,8 @@
 
 set -e -x
 
-base_dir="$PWD"
-src_dir="$base_dir/source-Osmocom"
+base_dir="$HOME/osmo-ci/coverity"
+src_dir="$PWD/source-Osmocom"
 cov_dir="$src_dir/cov-int"
 
 rm -rf "$src_dir"

jobs/coverity.yml

@@ -13,7 +13,7 @@
     node: coverity
     builders:
       - shell: |
-          cd $HOME/osmo-ci/coverity
+          cd coverity
           export PATH=$PATH:/opt/coverity/current/bin
           ./jenkins.sh
     publishers: