Added pipe to head in LVERSION variable line to handle case of multiple lustre-client packages breaking variable

[AeonJJohnson]

The command to populate the LVERSION variable in the ./configure script (derived from autotools/m4/lustre.m4) breaks if the build system has more than one lustre-client package installed, such as lustre-client and lustre-client-dkms. If these two packages are installed the command that populates the LVERSION variable breaks as two packages cause a two line result as a variable. Test compilation to validate xattr.h fails and the configure script fails.

Adding a pipe to head -1 on the LVERSION (autotools/m4/lustre.m7 line 17) forces a single line output that properly populates the LVERSION variable.

I don't know that adding head -1 is the best approach but it works and as robinhood source stands now any build system where the lustre-client and lustre-client-dkms are installed will break.

[tl-cea]

Pushed to gerrithub for validation and landing: https://review.gerrithub.io/c/cea-hpc/robinhood/+/1200350