build: Do not link with pcmk libraries

Patch 4205de05fe337d1b1127fae302e6e6c2f0613ccf introduced better way to
check for pacemaker headers but also usage of PCMK_LIBS when linking
boothd.

This is not needed, because boothd uses just crm/services.h header file
for inclusion of OCF return codes, so patch removes the use of PCMK_LIBS.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>