e2fsprogs: disable build of e4defrag unless explicitly enabled

The e2fsprogs configure script enables the build of the e4defrag
utility by default. Disable it unless BR2_PACKAGE_E2FSPROGS_E4DEFRAG
is selected.

Also the --disable-blkid option is not recognized by the configure
script. Use --disable-libblkid instead.

Signed-off-by: Sven Neumann <s.neumann@raumfeld.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>