Add missing zfs-dracut RPM dependencies

The zfs-dracut package requires the hostid, basename, head, awk,
and grep utilities be installed.  The first three are provided by
coreutils but additional dependencies are required for awk and grep.

Reviewed-by: Manuel Amador (Rudd-O) <rudd-o@rudd-o.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #7729 
Closes #7747

rpm/generic/zfs.spec.in

@@ -214,6 +214,8 @@ Summary:        Dracut module
 Group:          System Environment/Kernel
 Requires:       %{name}%{?_isa} = %{version}-%{release}
 Requires:       dracut
+Requires:       /usr/bin/awk
+Requires:       grep
 
 %description dracut
 This package contains a dracut module used to construct an initramfs