[omnibus] Don't create RPM database if it doesn't exist already

On Linux distributions not using the RPM package manager
(Debian, Ubuntu, etc.), the rpm probe of OpenSCAP could
initialize the sqlite RPM database into the /var/lib/rpm,
directory, as a side effect.

This change adds a new patch "rpmdb-no-create" to the RPM package.

This patch changes the openDatabase function to prevent creation
of the RPM database when it doesn't exist already.

omnibus/config/patches/rpm/rpmdb-no-create.patch

@@ -0,0 +1,42 @@
+--- a/lib/rpmdb.c
++++ b/lib/rpmdb.c
+@@ -463,6 +463,11 @@ static int openDatabase(const char * prefix,
+     if (db == NULL)
+ 	return 1;
+
++    /* Don't create db if it doesn't exist already */
++    struct stat st;
++    if (stat(rpmdbHome(db), &st) < 0)
++        return 1;
++
+     /* Try to ensure db home exists, error out if we can't even create */
+     rc = rpmioMkpath(rpmdbHome(db), 0755, getuid(), getgid());
+     if (rc == 0) {
+diff --git a/lib/rpmts.c b/lib/rpmts.c
+index 7a717b87d..21a2d3bec 100644
+--- a/lib/rpmts.c
++++ b/lib/rpmts.c
+@@ -91,8 +91,6 @@ int rpmtsCloseDB(rpmts ts)
+
+ int rpmtsOpenDB(rpmts ts, int dbmode)
+ {
+-    int rc = 0;
+-
+     if (ts->rdb != NULL && ts->dbmode == dbmode)
+ 	return 0;
+
+@@ -101,13 +99,7 @@ int rpmtsOpenDB(rpmts ts, int dbmode)
+     /* XXX there's a potential db lock race here. */
+
+     ts->dbmode = dbmode;
+-    rc = rpmdbOpen(ts->rootDir, &ts->rdb, ts->dbmode, 0644);
+-    if (rc) {
+-	char * dn = rpmGetPath(ts->rootDir, "%{_dbpath}", NULL);
+-	rpmlog(RPMLOG_ERR, _("cannot open Packages database in %s\n"), dn);
+-	free(dn);
+-    }
+-    return rc;
++    return rpmdbOpen(ts->rootDir, &ts->rdb, ts->dbmode, 0644);
+ }
+
+ int rpmtsInitDB(rpmts ts, int perms)

omnibus/config/software/rpm.rb

@@ -49,6 +49,7 @@
   env["CFLAGS"] << " -fPIC"
 
   patch source: "0001-Include-fcntl.patch", env: env # fix build
+  patch source: "rpmdb-no-create.patch", env: env # don't create db if it doesn't exist already
 
   update_config_guess