INSTALL.Fedora, INSTALL.RHEL: Make instructions more explicit.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Flavio Leitner <fbl@redhat.com>
Acked-by: Pritesh Kothari <pritesh.kothari@cisco.com>
INSTALL.DPDK: fix a typo in remote line

Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Pritesh Kothari <pritesh.kothari@cisco.com>