Fix few issues according to fedora packaging guidelines

* Package does not run rm -rf %{buildroot} (or $RPM_BUILD_ROOT) at the
     beginning of %install.
* Buildroot is not present
     Note: Buildroot: present but not needed
* Package has no %clean section with rm -rf %{buildroot} (or
             $RPM_BUILD_ROOT)
     Note: %clean present but not required
* remove unused build dependency on autoconf

libtdb.spec

@@ -6,9 +6,7 @@ Summary: The tdb library
 License: LGPLv3+
 URL: http://tdb.samba.org/
 Source: http://samba.org/ftp/tdb/tdb-%{version}.tar.gz
-BuildRoot: %(mktemp -ud %{_tmppath}/%{name}-%{version}-%{release}-XXXXXX)
 
-BuildRequires: autoconf
 BuildRequires: libxslt
 BuildRequires: docbook-style-xsl
 BuildRequires: python2-devel
@@ -65,7 +63,6 @@ Python3 bindings for libtdb
 make %{?_smp_mflags} V=1
 
 %install
-rm -rf $RPM_BUILD_ROOT
 
 make install DESTDIR=$RPM_BUILD_ROOT
 
@@ -75,9 +72,6 @@ find $RPM_BUILD_ROOT -name "*.so*" -exec chmod -c +x {} \;
 
 rm -f $RPM_BUILD_ROOT%{_libdir}/libtdb.a
 
-%clean
-rm -rf $RPM_BUILD_ROOT
-
 %files
 %defattr(-,root,root,-)
 %{_libdir}/libtdb.so.*