Deb: Add missing installation step to Salsa-CI job for 10.5 upgrades

Add vital missing step to MariaDB 10.5 upgrade job to actually install
the new binary being built. Without this the test was happily passing all
the time but actually not testing the upgrade.

Also stop using oneliner syntax for the install step to make the debugging
of failing installs/upgrades from build logs easier.

NOTE TO MERGERS: This commit is made on 10.6 branch and can be merged to
all later branches (10.7, 10.8, ..., 11.0). If/when some jobs break, they
will be fixed per branch on follow-up commits.

debian/salsa-ci.yml

@@ -155,12 +155,12 @@ blhc:
   EOF
   apt-get update -qq
 
-.test-install: &test-install |
+.test-install: &test-install
   # Install MariaDB built in this commit
-  apt-get install -y ./*.deb
+  - apt-get install -y ./*.deb
   # Verify installation of MariaDB built in this commit
-  dpkg -l | grep -iE 'maria|mysql|galera' || true # List installed
-  mariadb --version # Client version
+  - dpkg -l | grep -iE 'maria|mysql|galera' || true # List installed
+  - mariadb --version # Client version
 
 .test-verify-final: &test-verify-final |
   mkdir -p debug # Ensure dir exists before using it
@@ -615,10 +615,7 @@ mariadb.org-10.5 to mariadb-10.6 upgrade:
     - apt-get update -qq
     - apt-get install -y mariadb-server-10.5
     - *test-verify-initial
-    # Install MariaDB built in this commit
-    # Verify installation of MariaDB built in this commit
-    - dpkg -l | grep -iE 'maria|mysql|galera' || true # List installed
-    - mariadb --version # Client version
+    - *test-install
     - service mariadb status # There is no init.d/mysql in MariaDB 10.5+
     - *test-verify-final
   variables: