Fix for: "Plugin auth_gssapi_client could not be loaded: /usr//usr/lib64/mariadb/plugin/auth_gssapi_client.so: cannot open shared object file: No such file or directory"

RHBZ: #1768143
Upstream commit that caused the issue: https://github.com/MariaDB/mariadb-connector-c/commit/11a2d03

It's a Regression of:
RHBZ: #1624533
Reproducer: https://jira.mariadb.org/browse/CONC-383

--- mariadb-connector-c-3.1.4-src/include/mariadb_version.h.in	2019-09-03 14:48:10.000000000 +0200
+++ mariadb-connector-c-3.1.4-src/include/mariadb_version.h.in_patched	2019-11-03 12:50:12.453574192 +0100
@@ -24,7 +24,7 @@
 #define MARIADB_PACKAGE_VERSION_ID @MARIADB_PACKAGE_VERSION_ID@
 #define MARIADB_SYSTEM_TYPE "@CMAKE_SYSTEM_NAME@"
 #define MARIADB_MACHINE_TYPE "@CMAKE_SYSTEM_PROCESSOR@"
-#define MARIADB_PLUGINDIR "@CMAKE_INSTALL_PREFIX@/@PLUGINDIR@"
+#define MARIADB_PLUGINDIR "@PLUGINDIR@"
 
 /* mysqld compile time options */
 #ifndef MYSQL_CHARSET